Up to now the convention’s great divide was between the large and small states. Today focus drifted toward the rift between north and south, non-slave vs. slave-holding states. The 3/5 rule and expected rapid population growth in the southwest disturbed some northern delegates. If slaves and whites filled new states as anticipated, southern states would soon dominate the House of Representatives.
Abruptly, yet understandably, the aristocratic Gouverneur Morris (PA), who recently recommended doing away with the states, turned about in support of equal state suffrage in the senate as a counterbalance to a fast-growing south. Only a northern state senate majority could check a southern majority in the house.
In the background lurked southern fear of northern state intentions over slavery and the Mississippi River. Spain closed the port of New Orleans to American shipping after our Revolutionary War. The confederation nearly blew up over a 1786 proposed treaty negotiated by John Jay of NY, and supported by northern states, that abandoned claims to the Mississippi River for 25-30 years in exchange for a commercial treaty with Spain. Extended closing of the Mississippi would stem the draw of northeastern populations westward as well as support both northeastern real estate values and the shipping industry. The treaty would open Caribbean markets to American shipping and Spain promised assistance with the Barbary Pirate problem.
Jay’s treaty only confirmed southern suspicions. To keep population and profits, northeast mercantile powers were willing to induce stillborn western states by sacrificing the commercial value of their lands. Fortunately, the treaty went nowhere despite the predominance of northern states in the confederation congress. Southern delegates fought off a vote in part by denying a quorum, of simply not attending sessions. Thanks to the mid-1780s mess over the Mississippi River, treaties must clear a two-thirds rather than a majority senate hurdle for ratification in our Constitution.
Southwestern immigration, northeastern shipping interests, and slavery illustrate the interconnectedness of issues as the convention thrashed out the representational basis of the new congress.
Pierce Butler (SC) broached an open secret, that if given a chance, certain northern elements would deprive the south of its slaves. The Constitution must protect their property.
On the other hand, if the new government encouraged unlimited immigration and growth in the southwest, Morris feared a southern state-instigated war with Spain over the Mississippi, which would expose New England and the middle states to naval predations.
James Wilson (PA) compared efforts to deny rights to new western states as Great Britain denied her American colonies their rights. There would be similar consequences. He did not agree that protection of property was the first duty of government. Numbers should dictate representation, for wealth had been tried and was found to be too difficult.
On the question to strike out wealth, and to establish population as the sole basis of representation in the House of Representatives, reapportioned by a regular census, passed 9-0.
Somehow, despite clear signs of dissolution, the convention held together as delegates continued to fit the various pieces of their Constitutional puzzle. Some seven weeks after convening, members finally settled on the basis of the House of Representatives: population and not wealth.