The U.S. Constitution is the supreme law of the United States that provides the framework for the U.S. government and defines its powers. It was drafted in 1787 in Philadelphia in response to weaknesses in the Articles of Confederation, including a weak federal government and lack of separation of powers. The Constitution established a representative democracy with three branches of government and a system of checks and balances to limit any one branch from becoming too powerful. It has been amended 27 times, including the first ten amendments known as the Bill of Rights.