The United States Senate website has an excellent resource to learn more about the history behind equal representation in the Senate and proportional representation in the House, the plan sometimes referred to as the “Great Compromise.”  You can also explore the debate at the Constitutional Convention over the length of term for Senators, qualifications of a Senator, the role of the President of the Senate and Senate officers, Senate impeachment trials, treaties, and nominations. 

https://www.senate.gov/artandhistory/history/common/briefing/Constitution_Senate.htm

Mark J. Molli, Associate Director, Center for Civic Education