Longmont began in an unusual way. In 1870, a group of prominent men in Chicago decided to start a new town in Colorado. To do this, they sold membership in the new town, called "The Chicago-Colorado Colony," and used the money to buy 60,000 acres of land in a carefully chosen site in northern Colorado. They brought people, lumber, and building materials to the barren site, and by 1871, a new town was built. They named it "Longmont," after nearby Long's Peak.

The City of Longmont currently has over 100 designated historic structures located throughout the City. A structure may be designated for preservation if it has historical, architectural or geographical importance to the community. Applications for designation are reviewed by the Historic Preservation Commission and approved by the Longmont City Council. There are several financial incentives available for designated structures, including tax credits for qualified rehabilitation and refunds for certain building permit fees.

The City of Longmont has two nationally registered historic districts (http://www.nationalhistoricalregister.com/CO/boulder/state.html). The purpose of these districts is to recognize areas that have special character and interest. The West Side Historic District (added 1987 - District - #86002846) is roughly bounded by Fifth Avenue, Terry Street, Third Avenue, and Grant Street. The East Side Historic District (added 1986 - District - #86002812) is roughly bounded by Long's Peak Avenue, Collyer Street, Fourth Avenue, and Emery Street.

The West Side Historic District, west of downtown Longmont, incorporates two neighborhoods, Thompson Park and Central School. Residences, reflecting a wide variety of architectural styles, primarily date from 1871 to 1930, with the most intense development occurring between 1900 and 1930.