Article Four of the United States Constitution in the context of "Territories of the United States"

The Constitution of the United States is the supreme law of the United States of America. It superseded the Articles of Confederation, the nation's first constitution, on March 4, 1789. Originally including seven articles, the Constitution defined the foundational structure of the federal government.

The drafting of the Constitution by many of the nation's Founding Fathers, often referred to as its framing, was completed at the Constitutional Convention, which assembled at Independence Hall in Philadelphia between May 25 and September 17, 1787. Influenced by English common law and the Enlightenment liberalism of philosophers like John Locke and Montesquieu, the Constitution's first three articles embody the doctrine of the separation of powers, in which the federal government is divided into the legislative, bicameral Congress; the executive, led by the president; and the judiciary, within which the Supreme Court has apex jurisdiction. Articles IV, V, and VI embody concepts of federalism, describing the rights and responsibilities of state governments, the states in relationship to the federal government, and the process of constitutional amendment. Article VII establishes the procedure used to ratify the constitution.

In the United States, state governments are institutional units exercising functions of government within the country’s federal system, alongside the federal government. Each U.S. state's government holds legislative, executive, and judicial authority over a defined geographic territory. The United States comprises 50 states: 9 of the Thirteen Colonies that were already part of the United States at the time the Constitution took effect in 1789, 4 that ratified the Constitution after its commencement, plus 37 that have been admitted since by Congress as authorized under Article IV, Section 3 of the Constitution.

In the United States of America, each state has its own written constitution. The Supremacy Clause of the Constitution of the United States (Article VI, Clause 2) establishes that the Constitution, federal laws made pursuant to it, and treaties made under the authority of the United States, constitute the "supreme Law of the Land", and thus take priority over any conflicting state laws. It provides that state courts are bound by, and state constitutions subordinate to, the supreme law.

The Tenth Amendment to the United States Constitution (part of the Bill of Rights) provides that "The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people." The Guarantee Clause of Article 4 of the Constitution states that "The United States shall guarantee to every State in this Union a Republican Form of Government." These two provisions indicate states did not surrender their wide latitude to adopt a constitution, the fundamental documents of state law, when the U.S. Constitution was adopted.

The equal footing doctrine, also known as equality of the states, is the principle in United States constitutional law that all states admitted to the Union under the Constitution since 1789 enter on equal footing with the 13 states already in the Union at that time. The Constitution grants to Congress the power to admit new states in Article IV, Section 3, Clause 1, which states:

In each act of admission since that of Tennessee in 1796, Congress has specified that the new state joins the Union "on an equal footing with the original States in all respects whatever". Previously, when Vermont was admitted in 1791, its act of admission said Vermont was to be "a new and entire member" of the United States.