Then in 1787 the Constitutional Convention in Philadelphia proposed the Constitution of the United States to replace the Articles on Confederation, and those same 13 former colonies became the first 13 states in the Union by following the procedure required for ratification of the Constitution in 1789-1790.
Since the first 13 states ratified the Constitution, 37 new states have been added by Congress. The Constitution gives Congress the power to admit new states to the Union. Four states have been carved out of the original 13 states, which required consent of the state legislature concerned.
- Vermont was formed from New York (1791)
- Maine from Massachusetts (1820)
- Kentucky from Virginia (1792)
- West Virginia from Virginia(1863)
Texas was an independent Republic that was admitted to statehood in 1845.
The remaining 32 states were territories claimed or acquired by the United States and governed by the federal government until admitted to the Union in accordance with the Northwest Ordinance tradition for the transition of U.S. citizen populated federal territories to statehood.
The legal and political process for integration of lands west of the 13 original states was an issue dating back to the British colonial period. The Northwest Ordinance was enacted under the Articles of Confederation in 1787 to provide for integration of the territory Northwest of the Ohio River claimed by the new American nation.
When the First Congress of the United States convened under the Constitution it re-enacted the Northwest Ordinance as the first U.S. territorial organizational statute or “organic act” for the territories that would become Ohio (1803), Indiana (1816) and Illinois (1818). Beginning with Tennessee in 1796 until the admission of Hawaii in 1959, the principles for temporary government of territories, application of the Constitution and for formation of a democratic government embodied in the Northwest Ordinance became a traditional model under which all federal territories inhabited by U.S. citizens and comparable to other states were admitted to the Union.
Puerto Rico is the only such territory in U.S. history to be treated less than equally with those territories already admitted as states.