Photograph of Cienega Creek east of Tucson, Arizona, facing northeast in 1880, showing the freshly laid tracks of the Southern Pacific Railroad running alongside the creek - represented here by a narrow, essentially treeless channel - before arroyo downcutting affected the watershed. The valley floor is covered by grasses and is free of mesquites and other woody plants, although shrubs are common on the adjacent uplands. Note the brush fence running along the ridge at right midground. This view supports the conclusion that Cienega Creek (Spanish for "marsh," or "swamp") once had high groundwater conditions that could have prevented woody vegetation from growing.