Maricopa is a city in Pinal County, Arizona, United States, thirty miles south of Phoenix in the Gila River Valley. As of 2007, its population is estimated to be 37,863 an increase of 36,823 over the 2000 census figure of 1,040. This makes it the second-largest city in the county and Arizona's nineteenth-largest city. Maricopa's annexation plans during the next decade are likely to result in major growth in both population and area.
Highways to Maricopa include State Route 238 and State Route 347. Maricopa lies approximately 15 miles west of Interstate 10 and 15 miles north of Interstate 8. MaricopaXPress, operated by the city and Pinal County, offers two roundtrips to Phoenix geared towards commuters.
California Zephyr railcar at the Maricopa, AZ Amtrak station
Maricopa is currently the nearest stop to Phoenix on Amtrak's Sunset Limited and Texas Eagle trains. The Maricopa depot opened in 2001, originally in a converted passenger rail car but now in a metal building.
Information provided from Wikipedia