As to why we have 2 US Senators per state:
Two Senators per State
The Senate of the United States shall be composed of two Senators from each State. [U.S. Constitution, Article I, section 3, clause 1]
During the summer of 1787, the delegates to the Constitutional Convention in Philadelphia established equal representation in the Senate and proportional representation in the House of Representatives. Called the “Great Compromise” or the “Connecticut Compromise,” the unique plan for congressional representation resolved the most controversial aspect of the drafting of the Constitution.
In the weeks before the Constitution’s framers agreed to the compromise, the delegates from the states with large populations argued that each state’s representation in the Senate should correspond to the size of the state. Large-state delegates promoted James Madison’s Virginia Plan, the document that was the basis for several of the clauses in the Constitution. Under this plan, the Senate and the House would base their membership on the same proportional “right of suffrage.” That is, the number of senators in each state would be determined by its population of free citizens and slaves. Large states, then, stood to gain the most seats in the Senate. As justification for this advantage, delegates noted that their states contributed more of the nation’s financial and defensive resources than small states, and therefore, required a greater say in government.
Small-state delegates hoped to protect states’ rights within a confederate system of government. Fearing the effects of majority rule, they demanded equal representation in Congress, as was practiced under the Articles of Confederation and assumed in William Paterson’s New Jersey Plan. In fact, some framers threatened to withdraw from the convention if a proportional representation measure passed.
Other delegates sought a compromise between large-state and small-state interests. As early as 1776, Connecticut’s Roger Sherman had suggested that Congress represent the people as well as the states. During the 1787 convention, Sherman proposed that House representation be based on the population, while in the Senate, the states would be equally represented. Benjamin Franklin agreed that each state should have an equal vote in the Senate except in matters concerning money. The convention’s grand committee reported his motion, with some modifications, to the delegates early in July. Madison led the debates against Franklin’s measure, believing it an injustice to the majority of Americans, while some small-state delegates were reluctant even to support proportional representation in the House. On July 16, delegates narrowly adopted the mixed representation plan giving states equal votes in the Senate within a federal system of government.
Once delegates established equal representation in the Senate, they needed to determine how many senators would represent each state. State constitutions offered some guidance. Several states designated one senator per county or district, while in Delaware there were three senators for each of the three counties. Convention delegates did not refer to the state precedents in debate, however. Instead, they seemed to take a common-sense approach in deciding the number of senators.
According to constitutional commentator Joseph Story (1779-1845), few, if any, delegates considered one senator per state sufficient representation. Lone senators might leave their state unrepresented in times of illness or absence, and would have no colleague to consult with on state issues. Additional senators, moreover, would increase the size of the Senate, making it a more knowledgeable body, and better able to counter the influence of the House. On the other hand, a very large Senate would soon lose its distinctive membership and purpose, and actually decrease its ability to check the lower house or to allow senators to take personal responsibility for their actions.
Given these considerations, delegates had a limited choice regarding the number of senators. During the convention, they briefly discussed the advantages of two seats versus three. Gouverneur Morris stated that three senators per state were necessary to form an acceptable quorum, while other delegates thought a third senator would be too costly. On July 23, delegates filled in the blank in the proposal offered by Morris and Rufus King: “That the representation in the second branch consist of _____ members from each State, who shall vote per capita.” Only Pennsylvania voted in favor of three senators. When the question turned to two, Maryland alone voted against the measure, not because of the number, but because Martin disagreed with per capita voting, which gave each senator, rather than each state, one vote.
In its final form, the clause in the Constitution is deceptively simple. “The Senate shall be composed of two senators from each state” appears to be a single provision, the designated number of senators per state. Delegates agreed to this number, however, only after they had considered a larger matter: legislative representation. While representation proved to be the most controversial issue in the convention, delegates determined the number of senators quickly and with little dispute.