sentences:  From 1864, the Yuma Quartermaster Depot, today a state historic park, supplied all forts in present-day Arizona, as well as large parts of Colorado and New Mexico.After Arizona became a separate territory, Yuma became the county seat for Yuma County in 1871, replacing La Paz, the first seat.The Southern Pacific Railroad bridged the river in 1877, and acquired George Alonzo Johnson's Colorado Steam Navigation Company, the only steamboat company on the river.