The City of Lafayette is a home rule municipality located in southeastern Boulder County, Colorado, United States. The city population was 30…The City of Lafayette is a home rule municipality located in southeastern Boulder County, Colorado, United States. The city population was 30,411 at the 2020 United States Census. Lafayette is located in southeastern Boulder County. It is bordered by the town of Erie to the north and east, by the city of Broomfield to the east and south, and by Louisville to the southwest. U.S. Highway 287 is the main road through the city, leading north to Longmont and south to Broomfield and Denver. State Highway 7 leads east from Lafayette to Brighton and west to Boulder. There is also an exit off Interstate 25 to the city.