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.
The state takes its name from the Ohio River. The name originated from the Iroquois language word ohi-yo, meaning "great river" or "large creek". Partitioned from the Northwest Territory, the state was admitted to the Union as the 17th state (and the first under the Northwest Ordinance) on March 1, 1803. Ohio is historically known as the "Buckeye State" after its Ohio buckeye trees, and Ohioans are also known as "Buckeyes".