When considering what size each chamber of the legislature should be, most of the delegates were agreed in principle, though they varied greatly as to how their principles should be applied in practice. The Lower House, since it was meant to represent the needs, interests, and rights of the whole people, should be a fairly large body of legislators in order to fairly represent so large a body of citizenry. The Upper House, on the other hand, was meant to act more like a wise council of elders; it would therefore operate best as a small body, one that fostered cool and dispassionate deliberation. In the opening days of the Convention, Edmund Randolph—as the public face of the Virginia Plan—was called upon to explain what he had in mind as to the number that should occupy the second branch. He gave it as his opinion “that it ought to be much smaller than that of the first; so small as to be exempt from the passionate proceedings to which numerous assemblies are liable.” Let the Lower Chamber be the large, noisy, boisterous one—all the better for allowing everyone’s voice to be heard in the democratic House of Representatives. But let the aristocratic Senate be small and dignified, so that it may check the passionate proceedings of the Lower House when needed.
The debates over the size of the Senate were tied almost exclusively to the question of whether it should represent the states proportionally or equally. Those who advocated a proportional representation in the Senate hinted, on several occasions, that the smallest states would probably get no representatives at all in this branch. The reason for this exclusion was (as almost everyone agreed) that a good Senate must be a small body. If the Senate were proportioned among the states according to population or wealth, and if the smallest states were represented by even one Senator, then the total number of senators would be too large.
Once the states had agreed to an equal representation in the Senate, fixing the number of senators was not contentious. Gouverneur Morris proposed on July 23 that each state be allowed three senators, since “he wished the Senate to be a pretty numerous body.” He had very few supporters in that wish, however. Other delegates protested that that number would make the Senate too large, especially as new states would be added. When it came up for a vote, only Pennsylvania voted to have three senators from each state. The counter-suggestion—that each state have two senators—was agreed to unanimously. This number would make the first Senate a cozy 26-member chamber (assuming that all 13 states ratified the Constitution).
Debates over the size of the Lower House were more nuanced. It had been decided very early in the Convention and with overwhelming support that the Lower House should be proportioned to the population of each state, counting slaves as three-fifths of all free persons. The size of that body, then, would depend on how many inhabitants each congressman would represent (for instance, one congressman for every 5,000 residents would result in an enormous body; whereas one congressman for every 100,000 residents would result, like the Senate, in a very small body). In July, the same committee that recommended the “Great Compromise” (proportioning one house of Congress to the population and making the other house equal among the states) likewise for the first time suggested a precise number for the ratio of the Lower House. It specified: “That in the 1st. branch of the Legislature each of the States now in the Union shall be allowed 1 member for every 40,000 inhabitants” (factoring in the three-fifths clause that had already been agreed upon and specifying that every state should have at least one representative, even if their population was less than 40,000).
There were some objections to this proposal, but they were primarily from those members who had always wanted to see property factored into the apportionment and not merely population. After some discussion in favor of including property, Williamson reintroduced the rule of population, which included the three-fifths provision for slavery already agreed to in the Committee of the Whole, and added to it a provision that would require a periodic census in order to require Congress to reapportion on a regular basis. The Convention finally decided to readopt the rule tying representation to population alone, including the three-fifths clause.
The Committee of Detail which reported on August 6 had therefore unobtrusively reinserted the ratio of representatives “at the rate of one for every forty thousand.” When that article was debated, two objections arose. The first was voiced by Madison; he objected to the ratio “as a perpetual rule. The future increase of population, if the Union should be permanent, will render the number of representatives excessive.” Everyone was agreed that this body should be a large one, but still, it was possible to be too large. With the natural increase in size of the country, the membership would eventually become enormous. (If that same ratio were in place today, then the House would have nearly 8,000 members). Gorham tried to allay Madison’s fears: “It is not to be supposed that the government will last so long as to produce this effect. Can it be supposed that this vast country, including the western territory, will, one hundred and fifty years hence, remain one nation?” The other delegates, however, chose not to put their trust in the country’s dissolution to solve the problem that a fixed ratio would eventually cause, and it was agreed without dissent “to insert the words ‘not exceeding’ before the words ‘one for every forty thousand.’” This flexible standard would enable Congress to adjust the size of its own members downward from that ratio, but not upwards.
The other objection related to the number itself; many members thought that the body should be larger than the ratio would allow. Even Hamilton—who frequently said disparaging things about popular forms of government—agreed. He said that “he held it essential that the popular branch of [government] should be on a broad foundation. He was seriously of opinion, that the House of Representatives was on so narrow a scale as to be really dangerous, and to warrant a jealousy in the people for their liberties.” But this objection came late in the Convention, on September 8, and the Framers were by this time weary of debate. The motion to reconsider the number failed on a close vote. But the story did not end there.
On the last day of the Convention, after all of the other important matters had been settled, Nathanial Gorham rose to ask that the number of representatives be increased by replacing the number forty thousand with thirty thousand. Then a remarkable thing happened. The president of the Convention, George Washington, entered into the debates for the first time. He said that, owing to his position, he had maintained his silence throughout the Convention, “yet he could not forbear expressing his wish that the alteration proposed might take place.” Some members had believed that the small size of the representative body was a threat to the rights and interests of the people, and “he acknowledged that it had always appeared to himself among the exceptionable parts of the plan; and, late as the present moment was for admitting amendments, he thought this of so much consequence, that it would give him much satisfaction to see it adopted.” When the most revered man in the country expresses his personal wish to make a slight alteration for the sake of protecting the rights of the people, he does not speak in vain. The Convention exchanged the 40,000 figure for 30,000, and they did so unanimously and without a murmur of protest. To put these numbers in perspective, following the figures from the 1790 census (and not doing any rounding up) the total number of representatives in the House would be increased from 76 members to 105.