City of Aurora is a Home Rule Municipality spanning Arapahoe, Adams, and Douglas counties in Colorado. Aurora is an eastern suburb of the Denver-Aurora-Broomfield, CO Metropolitan Statistical Area (Metro Denver). The city is the third most populous city in the Colorado and the 56th most populous city in the United States. The city had a population of 325,078 in the 2010 Census.Denver and Aurora are the principal cities of the Denver Metropolitan Area which in 2007 had an estimated population of 2,464,866. (22nd most populous MSA) However, Denver and Aurora combined make up less than half of the Metro Denver Area's population and Aurora has approximately half the population of Denver. The estimated population of the Metropolitan Denver was 2,998,878 in 2007(15th most populous CSA).