What 1787 agreement created the U.S. Congress’s two-house structure?

The 1787 agreement that created the U.S. Congress’s two-house structure was the Connecticut Compromise.

Also called the Great Compromise, it resolved a dispute at the Constitutional Convention over legislative representation. Large states favored representation based on population, while small states wanted equal votes for each state.

The compromise created a bicameral Congress. In the House of Representatives, representation would be based on population; in the Senate, every state would have two senators. Roger Sherman and Oliver Ellsworth of Connecticut were central to the proposal.

The arrangement remains a defining feature of the U.S. Constitution. It differs from the Three-Fifths Compromise, which addressed how enslaved people would be counted for representation and taxation. It also differs from later agreements such as the Missouri Compromise and the Compromise of 1850.