The state was named for the Colorado River, which Spanish travelers named the Río Colorado for the ruddy (Spanish: colorado) silt the river carried from the mountains. The Territory of Colorado was organized on February 28, 1861, and on August 1, 1876, U.S. President Ulysses S. Grant signed Proclamation 230 admitting Colorado to the Union as the 38th state. Colorado is nicknamed the "Centennial State" because it became a state a century after the signing of the United States Declaration of Independence.
In January 1776, it became the first of the British North American colonies to establish a government independent of the Kingdom of Great Britain's authority, and it was the first to establish its own state constitution. Six months later, it became one of the original 13 states that founded the United States of America, and in June 1788 it was the ninth state to ratify the Constitution, bringing that document into effect.