Denver is a city in Bremer County in the U.S. state of Iowa. The population was 1,627 at the 2000 census. It is part of the Waterloo–Cedar Falls Metropolitan Statistical Area. Denver was originally called Jefferson City, but after the Star Mail Route, a mail service provided to towns having no federal service, was established, the town changed its name to Breckenridge. When a federal post office was established in 1863, the name was changed to Denver.