Something different today, Gentle Readers. I undertook a light research project the past few weeks, at the suggestion of one of the mods over at Reddit’s AskHistorians. African slaves did not arrive in the New World on their own. It took Africans capturing and enslaving them, moving them to ports, and then Europeans buying and transporting them across the ocean. The lion’s share of that traffic in the later decades of the Atlantic trade took place on British-flagged vessels until 1808, and thence forward under Portuguese registry. Every seafaring power got a finger in the pie at some point, the United States included. Most of the American vessels that plied the trade did not, as one might imagine, come from South Carolina. Instead, slavers hailed primarily from New England. Yankee shipwrights built their vessels, owned them, crewed them, invested in them, and profited from their voyages. Did that investment have any influence on the eventual debates over banning slave importation on January 1, 1808? I set off to find out. I also used a more conversational, casual tone than I usually do here.
The Short Version
It’s complicated and the context matters. The short version is “probably a little, but some and some decisive stuff back earlier.” Ok then, everyone’s satisfied so we can all go home, consume the beverages of our choice, and call it good. Or we could go deeper.
The Long Version
Right then, let’s roll the clock back to Philadelphia, 1787. It’s summer, that time of year when rich white guys sit down to fix the Articles of Confederation, good and hard. The Committee on Detail gets to work based on general things settled by the convention. Its members are John Rutledge (SC), Edmund Randolph (VA), James Wilson (PA), Nathaniel Gorham (MA), and Oliver Ellsworth (CT). That’s two New Englanders, two Southerners, and a dude from Pennsylvania. The rest of the convention takes a break while they go to work, but not before Charles Pinckney (SC) tells everybody that
“that if the Committee should fail to insert some security to the Southern States ag[ain]st an emancipation of slaves, and taxes on exports, he sh[oul]d be bound by duty to his State to vote ag[ain]st their Report.”
Waldstreicher, David. Slavery’s Constitution: From Revolution to Ratification (p. 89). Farrar, Straus and Giroux. Kindle Edition.
As if they could have forgotten.
The Committee on Detail’s report bans taxes on exports and slave imports, and by the way there’ll be no banning of those slave imports either. A few clauses down is a requirement for a two-thirds majority to pass any acts which would regulate trade, “navigation acts” in the parlance of the time. That first appears in Rutledge’s hand. Together this tilts wildly Southern: The South’s exports can’t be taxed. Its slave imports can’t be taxed. What can the South do that would get taxed? It’s either excise taxes, which had gone not so well previously, or a tax on imports that be a drain on shipping. Who did the shipping? New England, New York, and Philadelphia, mostly.
This was enough to get some pretty serious debate going. The arguments against involved much of the obvious: the Constitution they were drafting was proslavery. The 3/5 compromise would promote slave imports, since the South could literally buy votes in the House and Electoral College. If slavery weakened the South by requiring more military spending to keep it together, as the section sometimes argued, then the whole union would be on the hook. And really, we fought a revolution for freedom and now we’re going to protect slavery?
Rutledge, who chaired the Committee on Detail, gets up and argues otherwise: Hey, we’re not saying import slaves. We’re saying importing slaves shouldn’t be forbidden. Two, the South doesn’t need your dirty Yankee help protecting itself. The fact that we’re all paranoid about slave revolts and sore at how the British made off with so many of our slaves? Doesn’t count. But ultimately:
Religion & humanity had nothing to do with this question. Interest alone is the governing principle with nations. The true question at present is whether the South[er]n States shall or shall not be parties to the Union. If the Northern States consult their interest, they will not oppose the increase of Slaves which will increase the commodities of which they will become the carriers.
Waldstreicher, David. Slavery’s Constitution: From Revolution to Ratification (pp. 94-95). Farrar, Straus and Giroux. Kindle Edition.
Rutledge said what everybody knew. There was a kind of alliance between New England and the Lower South operating. Ellsworth helped prove it by calling the antislavery element out for hypocrisy. If slavery was wrong, why were they just banning the import of slaves? This from a guy from Connecticut.
The convention soon found they were at a serious impasse, so they got together another committee to work out a compromise: Yes to a tax on slave imports but it couldn’t go higher than the average of existing duties. No ban on slave imports permitted until 1800. Cool? Not cool. South Carolina moved to kick the date back to 1808. The change passed with the votes of New England, the Lower South, and Maryland.
Since New England was being so nice about the slave trade, the Carolinians flipped on the navigation act clause, which was then deleted. We end up with this, the slave trade clause:
The Migration or Importation of such Persons as any of the States now existing shall think proper to admit, shall not be prohibited by the Congress prior to the Year one thousand eight hundred and eight, but a Tax or duty may be imposed on such Importation, not exceeding ten dollars for each Person.
New England gets commerce-regulating power that it wants and the Lower South does not. The Lower South and New England team up to save the slave trade they’re both interested in.
As everything subsequent in this post flows in one way or another from those words, let’s unpack them a little. You have the usual constitutional circumlocution around slavery. The framers were sensitive to the notion that the Constitution would not explicitly sanction what they called “property in man”. This fooled no one, but the distinction would eventually become very important in antislavery constitutionalism largely thanks to the efforts of Salmon P. Chase and James G. Birney, but getting well outside the scope of the question. (Fair game for follow-ups or subsequent questions, of course.)
The key parts:
- Congress will have the power, come 1808, to impose a total ban on the importation of slaves to the United States.
- Congress does not have that power until 1808, though it may impose a tax of up to ten dollars a head on such imports. Congress could literally make that the first act of the first Congress, pass it on the first day, and have it be the first thing to cross George Washington’s desk.
- The clause applies to states, not to the United States in general. Congress can do whatever it likes with regard to territories. It can even ban taking slaves already in the US into territories. It will do so, banning the import of slaves to the Northwest, Mississippi, and Orleans Territories. Only the first of these bans is well known, and then as an absolute prohibition. That’s how it was written, but the choice of the first governor and indifference in Washington ensured it was never more than a questionably-secure ban on imports. The bans on imports to Mississippi territory (modern MS and Alabama, mostly) and Orleans (Louisiana, naturally) were more explicitly that, but only in effect briefly and are allowed to lapse. These precedents are relevant to later antebellum stuff, but again that takes us well past the bounds of the question.
- The clause allows Congress to exercise its power to ban the importation of slaves to the United States in general on, or at any point after, January 1, 1808. It’s not required to do so on that date or any other.
- None of this requires states to import slaves. All of them had enacted bans on it during the Revolution as part of the non-importation movement. But those bans were state law and could be reversed. They would be by Georgia (1787-98), North Carolina (1790-4), and of course South Carolina (1805-7).
Incidentally, all of these constitutional provisions are unamendable. They’re entrenched in the Constitution to exactly the same degree as the two senators per state rule.
That’s the lay of then land when the first Congress gets together. It took them literally thirteen days into the Washington presidency to get into a fight over slavery. Josiah Parker, of Virginia, got up in the House and suggested: hey, we have the authority in plain English to impose a ten dollar tax on slave imports right now. Why don’t we tax the crap out of them? In the ensuing debate representatives from Georgia and South Carolina made arguments that sounded downright 1850s, up to and including early attempts at a positive good defense of slavery. James Jackson (no relation that I’m aware of to Andrew or Thomas) of Georgia condemned it as “the most odious tax Congress could impose.”
That’s very far from New England, though. Roger Sherman, of Connecticut Compromise fame (and, you know, Connecticut) opposed Parker’s proposal on the grounds that it was an amendment to a general tariff bill. It really ought to come as its own bill, even though a tariff is exactly what Parker was proposing. The objection might sound a little suspicious, and maybe it was, but it was held so generally in the House that Parker agreed to withdraw his amendment and resubmit it as a freestanding bill.
Parker’s tax came back up and the House voted to postpone it to the next session, at which point it would get mixed up in a firestorm over antislavery petitions from some Quakers and Ben Franklin who also wanted the Congress to do something about the slave trade. Franklin’s petition asked that they “step to the very verge” of their power and…and maybe think about freeing any slaves illegally imported? The prospect of the United States government turning into an agent for active emancipation must have been wildly popular in the South, right? You’d expect the kind of slightly manic cheer that fills media aimed at very young children or certain hygiene products. History’s full of heartbreaking stuff, though. The Lower South went ballistic.
It didn’t get them much. A House committee took in the petitions and reported out a summary of Congress’ powers with regard to slavery. That report laid out much of what I summarized above, particularly that no ban would come before 1808. It also established accepted constitutional wisdom, even by Republicans, all the way to 1860:
- The Congress had no power to interfere with slavery in any way within the bounds of a state, either to emancipate the slaves or to regulate their treatment. However…
- Congress had the power to prohibit US citizens from carrying slaves to foreign ports and
- Could prohibit foreigners from setting up slavers for voyages in US ports, plus
- Congress could set standards for the treatment of slaves on ships bound for the US.
This report didn’t become law of any kind; the Senate never signed off on it. But the House as a whole endorsed it, over Southern objections, and antislavery societies took it as a how-to for their future slavery fighting.
Let’s look at items #2 and #3. This is a part of the slave trade that is almost invisible in the story of American antislavery, but it’s an important one. Remember above that the Constitutional restrictions apply to importation of slaves to the United States. They do not apply in any way to operations in the carrier trade, taking slaves from Africa to Cuba (mostly), the West Indies (number two), or ports in South America (fairly rare, but it happened).
That’s actually where most American slavers did their business. They were primarily New Englanders. We can narrow that down still further. The majority of American slave ships (~70%) were owned and built in Rhode Island. There were operations elsewhere in New England and in New York that registered on the contemporary radar, but the Rhode Islanders were conspicuously all over this. The trade was a major factor in their state’s economy in a way that it no longer was elsewhere, if it had ever been. (I honestly don’t know. Colonial-era slaving is well outside my expertise.) About two-thirds of their voyages brought slaves from Africa, mostly in exchange for rum distilled right back home in the smallest state, and took them to the Caribbean. The other third supplied the American South, but most slave imports to the United States arrived on foreign ships.
So here we have an explicit declaration of congressional power over a trade which isn’t actually that important to the South, since they get their slaves from foreigners, and which limiting would only really hurt Rhode Island. Thus, there’s some real action…eventually. Congress took until 1794, but then they passed the Slave Trade Act of 1794. George Washington put his John Hancock on it on March 22.
What’s the law do? American citizens, and anybody setting out from a US port, are prohibited
for himself or any other person whatsoever, either as master, factor or owner, build, fit, equip, load, or otherwise prepare any ship or vessel […] for the purpose of carrying on any trade or traffic in slaves, to any foreign country; or for the purpose of procuring, from any foreign kingdom, place or country, the inhabitants of such kingdom, place or country, to be transported to any foreign country, port, or place whatever, to be sold of or disposed of, as slaves
Do that particular dirty deed and your ship and all its accessories could be libeled, condemned, and forfeited to the United States in whatever district or circuit court happened to have jurisdiction. Furthermore, if you were involved with this sort of business, or aiding and abetting, you would take a $2,000 fine to be split between the United States and whoever prosecuted you. If you were a owner or master of a ship and even looked dodgy, and someone reported you to the customs officials, you could be required to swear an oath and give a bond that you would not embark any African or other natives to take elsewhere and sell as slaves for the following nine months. Congress wasn’t quite done yet. It also assessed a $200 per-head fine on any slaves you tried to traffic in, again split halfsies between the US and the prosecution.
You might anticipate a big controversy here and a law that just squeaked by, but it doesn’t seem so. I went looking for debates and the roll-call vote on the measure, but couldn’t find them. Don Fehrenbacher tells me that the law got “ready acceptance […] in both houses”. I’m inclined to believe him, but his footnote led me to a dead end. This is all in the Annals of Congress, which were compiled retrospectively from newspaper accounts decades later rather than recorded live, as it were. So it’s possible a debate happened and no one took much notice, but I’ve spent a couple of hours looking and I can’t even give you the vote totals. Beats me. (If anybody has found records of this stuff, please let me know; I’m desperately curious.) The law was, Fehrenbacher says, the result of some very carefully written antislavery petitions. In particular, they took great pains to avoid any request for abolition.
So the 1794 act becomes law. It’s not the most draconian thing, but the fines are quite high. It lacks for a good enforcement regime, though. Basically you’re looking at private prosecutions, which half the fine would buy the government. Those would mostly have to happen in the very places where the trade was most popular and its wealthy practitioners most influential. Long odds, right? Maybe, maybe not. It was enough to get Cyprian Sterry, one of Providence’s slaving bigwigs, to quit the business when the local antislavery groups promised to come after him.
And then there’s John Brown. No, not that John Brown with the wild beard and the badass mural in Kansas. (But seriously, look at that mural!) John Brown of the Brown University Browns. John Brown is having none of this crap about fines. The Congress can take its slave trade act and shove it. He’d been doing the same thing with Rhode Island’s state law against slave trading voyages since 1787. He sent a ship, the Hope, off a-slaving. Hope called at the Guinea coast, bought some people, and took them off to Cuba where the sale of the 229 survivors turned a handy profit.
Brown had clearly fitted out and set off a slaving voyage. His brother Moses, a Quaker convert, and the local Abolition Society came after him in a private prosecution. They made it their business to do this, but usually things got to the point where someone would sign an agreement to renounce the trade (as Sterry did) and they would drop the prosecution. Negotiations to that end did not budge Brown at all. Moses threatened him with more than the loss of an older ship if he kept at things, but Brown sucked up the loss of the Hope. Eventually it became clear that Brown was trying to push things to trial. If someone got nailed for illegally importing slaves they would have to face a jury, and a Rhode Island jury would probably not convict. Once that became an established fact, the law would be a dead letter.
Which it was, for the most part. The Washington administration did not bend over backwards to see the law enforced. Rhode Island’s commerce dipped for a year after passage, but then came right back. Between 1794 and 1804, Rhode Island saw twenty-two prosecutions but we know of at least two hundred voyages to Africa in the same time. It seems that the volume of the trade significantly increased after it became illegal. Good lawyering, friendly juries, and occasional intimidation kept it safe until Jefferson appointed one of the big name slavers to the customs post at Bristol in 1804. Shockingly, African clearances from there shot way up. Prosecutions did not.
I told you most of that to set this up. Come 1800, things are looking a little better for the 1794 law. The Adams administration is encouraging prosecutions and has a few ongoing. Congress decides to revisit things and improve on the old law with a supplementary bill. This one is going to jack the fines (double the value of vessels forfeited and price of the slaves), outlaw investment in slaving ventures (at the pain of losing twice your stake in them), and if you’re actually on the ship you could get two years’ jail. This applies to Americans doing their own trading destined for foreign ports, as well as Americans on board or investing in foreign vessels. If the Navy, or equivalent, does the capturing then its officers and crew are entitled to prize money. And if a private prosecution brings any of this about, the fines go halfsies to the US and the accuser again.
By this point, John Brown is 50% of Rhode Island’s House delegation. He has some things he needs to say. Quoting from the Annals of Congress here:
it [was] improper to prevent the citizens of the United States enjoying the benefits of a trade enjoyed by all the European nations. […] Many members of the House, he observed, knew how the former act was passed; they knew that Congress was drilled into it by certain persons who would not take *no* for an answer. It was well known that the Abolition Society, otherwise the Society of Friends, as they were called, were very troublesome until they got that act passed.
Cheeky of him to name the outfit his brother was a member of, and which had prosecuted him, by name. Brown went on to say that no American law forbade exporting Africans from Africa. So why not just let Americans take Africans where they pleased? Better to enjoy the proceeds than leave money laying on the table. They were slaves either way, ok? Cutting Americans out of such a lucrative business was just bad policy and, anyway:
it was wrong, when considered in a moral point of view, since, by the operation of the trade the very people themselves much bettered their condition.
He said it. Having crossed that Rubicon, which pitched him all the way down with the Lower South, Brown noted that Congress could fill up the Treasury with slave-produced revenues. Far better to do that then debt finance things, right? And it’s not like US law would prevent “one more slave” from being taken. It would just be some foreigner that did the taking. With distilleries idle, why not have the rum go off to buy people? Brown
had been well informed that on those coasts New England rum was much preferred to the best Jamaica spirits, and would fetch a better price.
This is, as I mentioned before, literally how Rhode Island bought slaves. Brown had been well informed by his own ledgers. I don’t know about Brown personally, but some of the traders owned their own distilleries.
I don’t know that any other New Englander spoke in opposition to the 1800 law. It passed on on May 10, 1800, clearing the house with all of five votes against. Who are those guys? Brown, of course, George Dent (MD), Joseph Dickson (NC), John Rutledge Jr. (SC), and Benjamin Huger (SC). It’s by no means a prefect indicator, but the fact that Brown alone votes against the bill paints him as a pretty marginal figure. The commerce is mostly a Rhode Island affair and the other Rhode Islander in the House didn’t vote against it. But one does have to consider that all previous acts turned out to be paper tigers. Even forfeited ships often got bought back by their previous owners for pittances. The 1800 revisions had as much effect as the 1794 original: a brief downturn followed by resumption and increase of voyages. Between the international situation and American non-enforcement, the US share of slave exports from Africa goes from an estimated 2% (1780s) to 9% in the following decade and then 16% for the first Jefferson administration.
Stephen Row Bradley
Skipping a few minor episodes (making imports of slaves to a state that has closed the trade a federal offense that inspires SC, along with the money to be made importing slaves for further transit to Louisiana, to reopen the trade and a revival of the ten dollar tax that goes nowhere in retaliation against SC) we get to 1808…almost. We have to come up for a moment in December of 1805, when a New Englander gets conspicuous again. Stephen Row Bradley, of Vermont, gets up in the Senate and suggests they get cracking on a bill to prohibit slave imports, effective the first of 1808. The time might have seemed ripe, with states calling for a constitutional amendment to permit banning slave imports then and there not that long before, but Bradley’s proposal was taken as too soon all the same. There’s an undercurrent of doubt in all of this as to whether it’s proper for Congress to even consider an import ban before 1808, let alone years in advance.
December, 1806. Jefferson’s annual message (the equivalent to our State of the Union) recommends that Congress get an import ban together, effective January 1, 1808. Jefferson defended getting it done in advance on the grounds that it would mitigate against catching any vessels en route who may have started out legal but become illegal in passage. Bradley introduces his bill on December 3. There’s a broad consensus that now’s the time to do something and a ban should happen at the first available moment. Southerners even carp at the suggestion that they want anything else. The fights start over the details, with there being three big ones:
- What to do with people imported illegally? Should they be freed? If so, what does the nation do with them? Take them home? Settle them somewhere? Or do they remain slaves to be sold at auction? And if so, by whom? Was the federal government to become a slave trading operation? (Decided by the local jurisdiction, which meant kept as slaves and sold by state governments in the South.)
- What kind of penalty should violators face? (Original version: fines and forfeiture. Seen by most of the North as too little. Amended: death. Split the North, with many feeling it was too much. Final version: jail time.)
- Should Congress regulate the domestic maritime trade in slaves? Later on, this is often called the coastwise trade. Most of it runs from the Chesapeake to South Carolina, Georgia, and eventually Mobile and New Orleans. (Yes, but not much.)
These debates are not heavily studied, at least as of Matthew Mason’s Slavery Overshadowed: Congress Debates Prohibiting the Atlantic Slave Trade to the United States 1806-1807 (2000). Even contemporaries paid far more attention to other issues, despite often fiery rhetoric. The distinction is very much sectional, though Mason notes that the South prevailed as usual with the help of some northern cooperation. He doesn’t call out any New Englanders as conspicuous. This nuts and bolts wrangling took place in the House. The Senate recorded no debates or votes -thanks a lot, jerks-. Peter Early (Georgia) and John Randolph (Virginia) were conspicuous on the southern side, but if there was a particular locus of resistance in the New England delegations Mason doesn’t note it and I think he would have.
On the key vote as to what would happen with those people imported illegally, the House came to a 60-60 tie broken by the Speaker (Nathaniel Macon, NC). It got to that point with thirteen northerners voting against their section, eleven of them from mid-Atlantic states. They were Joseph Clay (PA), Henry Livingston (NY), Josiah Masters (NY), Gurdon Mumford (NY), John Russel (NY), Martin Schuneman (NY), Uri Tracy (NY), Phillip Van Cortlandt (NY), Killian K. Van Rensselaer (NY), Daniel C. Verplanck (NY), Eliphalet Wickes (NY)
What about those other two? I had to do a little hunting here, since it’s one of those things where you have to figure out which side is which and which is the relevant vote. It’s here. My method: I recognize the names of several southerners on sight, particularly the hard-liners, and know the section voted pretty solidly one way. So we want the nays. To be doubly-sure, and do the further sifting, I compared the nays with the roster here (PDF). I came out with, in addition to the previous list, Samuel Tenney (NH) and Peleg Wadsworth (MA).
Both are New Englanders, though neither is a Rhode Island man. I don’t know if Tenney and Wadsworth had any personal or constituency connections to the slave trade or not. This isn’t quite an up or down vote against slavery, though it’s close, so there may have been tactical considerations involved too. The strong New York connection to southern interests, political and economic, must be a factor for the others. New York’s remaining slave population might have served as another, but I’ve got my doubts considering they can’t have expected a whole lot of slavers to aim for their ports and so end up depositing human cargo locally where it would matter on a personal level that much. What slave ship is going to take a hold even partially full of people to a state that passed gradual emancipation in 1799 when there are so many more hospitable and profitable ports?
Which brings us to regulation of the coastwise trade, with the question being whether to limit the trade to vessels displacing forty tons or more. Twelve Upper South men voted for it, only ten northerners opposed. This was a significant limitation, as while an Atlantic-going slaver would run around 158 tons, the coastwise trade involved mostly vessels smaller than that.
So let’s fine those dissenting Yankees again. The vote is here. We want the Nays. There are seven repeat offenders from the last vote here: Josiah Masters (NY), Gurdon Mumford (NY), Martin Schuneman (NY), Samuel Tenney (NH), Uri Tracy (NY), and Killian K. Van Rensselaer (NY). That leaves us three to find. They are Silas Betton (NH), Martin Chittenden (VT), Samuel Dana (CT). One wonders just what Martin Chittenden and Stephen Bradley said to each other when they got home.
So there’s four New Englanders in the mix, counting Tenney with the three new arrivals. That’s not a lot (35 New England reps total, 20 of them Federalists) but it is something. The New England of the very early 1800s is not the New England of the 1840s and 1850s. It’s a place where antislavery is popular, but it’s not the region-defining thing it would be in future years. That begins to emerge when it becomes clear that the Federalists are done as a national party and they don’t need to be appealing to enslavers anymore as their partners in Virginia and South Carolina in particular are no longer interested. I don’t know what’s going on with the Chittenden in Vermont at all, and Rhode Island is conspicuous in its absence (both RI reps are Republicans at the time, so maybe party whip and certainly the impotence of previous laws would be a factor), but they must have had their reasons. The state didn’t lose interest in slave trading for a while yet hereafter.
I fired up my Biographical Directory of the United States Congress to see if there was a partisan angle. All four are federalists. Party lines aren’t as hard as they would become, but they could be looking to keep alive a national Federalism by resisting Jefferson’s program in hopes of wooing back southern coalition partners. But it’s only an inclination, against the general trend of their party’s vote, and it’s not too long after this that the party try to position themselves as a New England sectional party with an antislavery bent. On the balance, and absent any meaningful biographical data about them, I don’t think partisanship is the main factor. I can’t say for sure that there are personal or constituency interests driving them, but it seems likely.
I haven’t gone looking in the debate myself to see if any of the against-the-grain guys spoke up in an interesting way, but between my sources I think if they said anything useful and it survived, I’d have seen it quoted. It’s rare for them to even be mentioned by name. Mason notes that for all the fireworks in Congress, the slave trade prohibition doesn’t seem to have drawn many eyeballs. With the exception of Bradley, few of the antislavery party even seem to have felt it was the main event of the Ninth Congress. (Though it was the big event of their generation of antislavery activism.) The papers took little interest, and the Annals were collected largely from newspaper reports, so things probably have slipped away.
The bill passes on March 2, 1807, which brings us to our last vote. Only five men vote to keep the trade open. It is actually open at this point, because SC still has it going. They are Silas Betton (NH), Martin Chittenden (VT), James M. Garnett (VA), Abram Trigg (VA), and David R. Williams (SC). No Rhode Islanders but two New Englanders willing to take it to the bitter end and go on record, both Federalists. Chittenden remains the real mystery to me. New Hampshire at least has a coastline. He was born in northwestern Connecticut, but left there when he was thirteen. That’s old enough to have opinions, maybe. He was educated at Dartmouth and may have picked up his position there, but that would be a question for his biographer.
It’s very likely that I’m forgetting some.
The Slaveholding Republic by Don Fehrenbacher on the mechanics of the slave trade and law in particular, but also John Brown.
James, Sydney V. Of Slaves and Rum. Reviews in American History 10.2 (1982): 168-72. Web. A book review that gives some details from The Notorious Triangle, about Rhode Island and the slave trade which I desperately want to read, but is well outside my research budget.
Mason, Matthew E. Slavery Overshadowed: Congress Debates Prohibiting the Atlantic Slave Trade to the United States, 1806-1807. Journal of the Early Republic 20.1 (2000): 59-81. Web for fine-grain details of the votes and debates.
Slavery & Politics in the Early American Republic by Mason was helpful or situating the New England Federalists.
Slavery’s Constitution: From Revolution to Ratification by David Waldstreicher for the Constitutional Convention and Yankee-Carolina alliance.
And a finding aid for the John Brown Papers (PDF) at the Rhode Island Historical Society for more information about Brown and how the Abolition Society operated.