The history of the legislative branch of the U.S. government predates the U.S. Constitution. The Continental Congress formed a sort of legislative government for the U.S. before, during and immediately following the Revolutionary War. In fact, under the Articles of Confederation -- America's first governing document -- Congress formed the entirety of the federal government.

Why this Presented Problems

One of the problems with the Articles of Confederation was that it gave Congress the responsibility of governing without giving it any power to actually enforce its legislation over the states. When the U.S. Constitution was written in 1787, its framers set out to give more power to the legislature while providing checks and balances in the form of the executive and judicial branches of government.

The Legislative Branch under the Constitution

Article I of the U.S. Constitution establishes the legislative branch of government and enumerates its responsibilities. These include introducing new laws, changing existing laws, declaring war, levying taxes and tariffs and setting the national budget. Article I establishes a legislature with two houses. Article I, Section 2 establishes the U.S. House of Representatives and Article I, Section 3 establishes the U.S. Senate.

Why We Have a Bicameral Legislature

The framers of the Constitution designed a bicameral legislature as a compromise between populous states, which wanted representation in Congress to be based on population and smaller states that wanted equal representation for each state. Each state has equal representation in the Senate and proportionate representation in the House of Representatives.