State governments in the United States are those republics formed by citizens in the jurisdiction thereof as provided by the United States Constitution; with the original 13 States forming the first Articles of Confederation, and later the aforementioned Constitution. Within the U.S. constitution are provisions as to the formation of new States within the Union.
Structured in accordance with state law (including state constitutions and state statutes), most state governments are modeled on the federal system, with three branches of government—executive, legislative, and judicial.
Under the Tenth Amendment to the United States Constitution, all governmental powers not granted to the federal government by the Constitution are reserved for the states or to the people.
The governments of the 13 colonies that formed the original union under the Constitution trace their history back to the royal charters which established them during the era of colonialism. Most other states were organized as federal territories or parts of other states before forming their governments and requesting admittance into the union. Notable exceptions are California, Vermont, Texas and Hawaii, which were sovereign nations before joining the union.