Colorado joined the United States on August 1, 1876, becoming the 38th state during the centennial year.
President Ulysses S. Grant signed Proclamation 230 admitting Colorado to the Union. The timing came only four weeks after the July 4 centennial, leading to Colorado’s enduring nickname, the “Centennial State.”
Colorado had previously been organized as a U.S. territory. Congress passed an enabling act on March 3, 1875, setting out the process and requirements for statehood. After the territory completed the necessary constitutional and governmental steps, admission followed in 1876.
Colorado’s statehood was not itself the anniversary being celebrated, but it became one of the most memorable national milestones associated with the centennial year. Arizona and New Mexico joined the Union much later, in 1912, while Wyoming became a state in 1890.