Why Does Congress Have Two Houses?

When the framers of the Constitution were creating a new government, representation was an issue near and dear to their patriotic hearts. After all, "No Taxation Without Representation" was a reason they'd just fought with Britain. They decided on a legislative branch with two houses, each with its own powers and limitations. Why did they choose this system? Which famous figures battled over this bicameral vision? Over 200 years later, how has it changed, and does it still fulfill their exp...