Monticello is a city in Jones County, Iowa, United States. The population was 3,607 at the 2000 census. It is part of the Cedar Rapids Metropolitan Statistical Area. For many years, U.S. Highway 151 went directly through Monticello. In 2004, a four lane bypass around Monticello was completed and opened. As a result, the highway was moved about a mile south of the previous route.