On August 1, 1876, President Ulysses S. Grant signed legislation admitting Colorado to the Union as the Centennial State (it was admitted 28 days after the 100th anniversary of the United States). When Spanish explorers first visited the region that is now Colorado in the 1600s, they found several different Indian groups already inhabited it. The Arapaho, Cheyenne, Comanche, Kiowa, and Pawnee tribes lived on the vast plains and the Utes lived in the mountain valleys. Failing to find gold, the Spaniards left without attempting to colonize the area. In 1682, French explorer Robert Cavelier, Sieur de la Salle, claimed an area that included present-day eastern Colorado. In 1706, Juan de Ulibarri claimed the region for Spain.