The most populous cities in area code 303 are: Denver, Aurora, Littleton, Longmont, and Arvada.
Other cities in the 303 area code include: Fort Lupton, Golden, Brighton, Englewood, Keenesburg, Hudson, Idaho Springs, Deer Trail, Louisville, Lyons, Byers, Allenspark, Sedalia, Bennett, Roggen, and Strasburg.
Denver, officially the City and County of Denver, is the capital and most populous municipality of the U.S. state of Colorado. Denver is in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains. The Denver downtown district is immediately east of the confluence of Cherry Creek with the South Platte River, approximately 12 mi (19 km) east of the foothills of the Rocky Mountains. Denver is nicknamed the Mile-High City because its official elevation is exactly one mile (5280 feet or 1609.3 meters) above sea level, making it the highest major city in the United States. The 105th meridian west of Greenwich, the longitudinal reference for the Mountain Time Zone, passes directly through Denver Union Station.Denver is ranked as a Beta- world city by the Globalization and World Cities Research Network. With a 2015 estimated population of 682,545, Denver ranks as the 19th-most populous U.S. city, and with a 2.8% increase in 2015, the city is also the fastest-growing major city in the United States. The 10-county Denver-Aurora-Lakewood, CO Metropolitan Statistical Area had an estimated 2015 population of 2,814,330 and ranked as the 19th most populous U.S. metropolitan statistical area. The 12-city Denver-Aurora, CO Combined Statistical Area had an estimated 2015 population of 3,418,876, which ranks as the 16th most populous U.S. metropolitan area. Denver is the most populous city of the 18-county Front Range Urban Corridor, an oblong urban region stretching across two states with an estimated 2015 population of 4,757,713. Denver is the most populous city within a 500-mile (800 km) radius and the second-most populous city in the Mountain West after Phoenix, Arizona. In 2016, Denver was named the best place to live in the USA by U.S. News & World Report.
Aurora is a Home Rule Municipality in the U.S. state of Colorado, spanning Arapahoe and Adams counties, with the extreme southeastern portion of the city extending into Douglas County. Aurora is one of the principal cities of the Denver-Aurora-Lakewood, CO Metropolitan Statistical Area (Metro Denver). 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-Lakewood, CO Metropolitan Statistical Area had an estimated population of 2,645,209 on July 1, 2012 (the 21st most populous MSA in the U.S.). However, Denver and Aurora combined make up less than half of the Denver Metro Area's population and Aurora has approximately half the population of Denver. The estimated population of Denver-Aurora, CO Combined Statistical Area was 3,214,218 on July 1, 2012 (16th most populous CSA).
Littleton is the Home Rule Municipality in Arapahoe, Douglas, and Jefferson counties that is the county seat of Arapahoe County, Colorado, United States. The city is a part of the Denver-Aurora-Lakewood, CO Metropolitan Statistical Area. The city population was 41,737 at the 2010 United States Census, ranking as the 20th most populous municipality in the State of Colorado.
The 303 area code lies within the Mountain Daylight Time Zone (or MDT). The current time in Mountain Daylight Time is 5:41 PM on Jun 09, 2023.