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.
South Dakota is bordered by the states of North Dakota (on the north), Minnesota (to the east), Iowa (to the southeast), Nebraska (on the south), Wyoming (on the west), and Montana (to the northwest). The state is bisected by the Missouri River, dividing South Dakota into two geographically and socially distinct halves, known to residents as "East River" and "West River".