The United States Constitution has endured for more than two centuries as the framework of government. However, the meaning of the Constitution has been changed by both formal and informal methods. There are many more informal methods than formal methods to change the Constitution because they include much simpler processes. The informal methods don't exactly change the Constitution; they change the way it is interpreted.

One formal method to change the Constitution is by passing a bill through both houses of Congress, with a two-thirds majority in each. Once the bill is passed it is sent to the states. This is the process used by all current amendments. Congress usually puts a time limit for the bill to be approved as an amendment. The second method is for a Constitutional Convention to be called by two-thirds of the state legislatures. The convention would propose one or more amendments to the Constitution. This method has never been used, but there has been much discussion as to what kind of changes this process would make to the Constitution.

An informal method to amend the Constitution would be judicial interpretation. Judicial interpretation includes reinterpretation of the Constitution. This has brought about some of the greatest changes in the Constitution, for example when Brown v. Board of Education in 1954 ended racial segregation. Presidential or Congressional action are other informal methods that may lead to change, for example when Thomas Jefferson used his authority to purchase the Louisiana Territory, even without clear authorization to do so. Congressional action was used when Congress passed the War Powers Act in 1973, attempting to restrict the foreign policy vote of the president.