Sentinel Peak is a 2,897 ft (883 m) peak in the Tucson Mountains southwest of downtown Tucson, Arizona. The valley's first inhabitants grew crops at the mountain's base, along the Santa Cruz River. The name "Tucson" is derived from the O'odham Cuk Ṣon [tʃʊk ʂɔːn], meaning "[at the] base of the black [hill]". In the 1910s, University of Arizona students used local basalt rock to construct a 160-ft-tall (49 m) block "A" on the mountain's east face, near its summit, giving the peak its other name, "A" Mountain. The peak is part of a 272-acre (110 hectares) park, the largest natural resource park in the City of Tucson.