Equal footing in the context of "List of states and territories of the United States"

Admission to the Union is provided by the Admissions Clause of the United States Constitution in Article IV, Section 3, Clause 1, which authorizes the United States Congress to admit new states into the Union beyond the thirteen states that already existed when the Constitution came into effect. The Constitution went into effect on June 21, 1788, in the nine states that had ratified it, and the U.S. federal government began operations under it on March 4, 1789, when it was in effect in 11 out of the 13 states. Since then, 37 states have been admitted into the Union. Each new state has been admitted on an equal footing with those already in existence.

Of the 37 states admitted to the Union by Congress, all but six have been established within existing U.S. organized incorporated territories. A state that was so created might encompass all or part of a territory. When the people of a territory or a region have grown to a sufficient population and have made their desire for statehood known to the federal government, Congress in most cases has passed an enabling act, authorizing the people of that territory or region to frame a proposed state constitution as a step toward admission to the Union. The use of an enabling act has been a common historic practice, but several states were admitted to the Union without one.

Article Five of the United States Constitution describes the procedure for altering the Constitution. Under Article Five, the process to alter the Constitution consists of proposing an amendment or amendments, and subsequent ratification.

Amendments may be proposed either by the Congress with a two-thirds vote in both the House of Representatives and the Senate; or by a convention to propose amendments called by Congress at the request of two-thirds of the state legislatures. To become part of the Constitution, an amendment must then be ratified by either—as determined by Congress—the legislatures of three-quarters of the states or by ratifying conventions conducted in three-quarters of the states, a process utilized only once thus far in American history with the 1933 ratification of the Twenty-First Amendment. The vote of each state (to either ratify or reject a proposed amendment) carries equal weight, regardless of a state's population or length of time in the Union. Article Five is silent regarding deadlines for the ratification of proposed amendments, but most amendments proposed since 1917 have included a deadline for ratification. Legal scholars generally agree that the amending process of Article Five can itself be amended by the procedures laid out in Article Five, but there is some disagreement over whether Article Five is the exclusive means of amending the Constitution.