The City of Aurora (, ) is a Home Rule Municipality located in Arapahoe, Adams, and Douglas counties, Colorado, United States. Aurora lies immediately east of Denver and it is one of the principal cities of the Denver–Aurora–Lakewood, CO Metropolitan Statistical Area and a major city of the Front Range Urban Corridor. The city's population was 325,078 in the 2010 census, which made it the third most populous city in the State of Colorado and the 54th most populous city in the United States.
The Denver-Aurora-Broomfield, CO Metropolitan Statistical Area had an estimated population of 2,645,209 on July 1, 2012 (the 19th most populous MSA in the U.S.) Denver and Aurora combined make up less than half of the metro area's population and Aurora has approximately half the population of Denver. The estimated population of the Denver-Aurora, CO Combined Statistical Area was 3,214,218 on July 1, 2012 (15th most populous CSA).