The Lower Basin states also sought to develop the Colorado for municipal supplies. Central Arizona initially relied on the Gila River and its tributaries through projects such as the Theodore Roosevelt and Coolidge Dams - completed in 1911 and 1928, respectively. Roosevelt was the first large dam constructed by the USBR and provided the water needed to start large-scale agricultural and urban development in the region. The Colorado River Aqueduct, which delivers water nearly from near Parker Dam to 10 million people in the Los Angeles metropolitan area, was completed in 1941. The San Diego Aqueduct branch, whose initial phase was complete by 1947, furnishes water to nearly 3 million people in San Diego and its suburbs. The Las Vegas Valley of Nevada experienced rapid growth in part due to Hoover Dam construction, and Las Vegas had tapped a pipeline into Lake Mead by 1937. In 2018 a second and lower tunnel was completed to continue furnishing water to Las Vegas. Nevada officials, believing that groundwater resources in the southern part of the state were sufficient for future growth, were more concerned with securing a large amount of the dam's power supply than water from the Colorado; thus they settled for the smallest allocation of all the states in the Colorado River Compact.