The City and County of Denver is the capital and the most populous city of the U.S. state of Colorado. Denver is a consolidated city-county, located in the South Platte River Valley on the High Plains, just east of the Front Range of the Rocky Mountains. The United States Census Bureau estimated that the population of Denver was 610,345 in 20, making it the 24th most populous U.S. city. It is the largest city within a 500-mile (800km) radius and the second-largest city in the Mountain West after Phoenix. Denver's economy is based partially on its geographic position and its connection to some of the major transportation systems of the country. Because Denver is the largest city within 500miles (800km), it has become a natural location for storage and distribution of goods and services to the Mountain States. Denver's position near the mineral-rich Rocky Mountains encouraged mining and energy companies to spring up in the area. In the early days of the city, gold and silver booms and busts played a large role in the economic success of the city.