The City of Longmont is a Home Rule Municipality in Boulder and Weld counties of the U.S. state of Colorado. Longmont's population was 86,270 at the time of the 2010 U.S. Census.
Longmont was founded in 1871 by a group of people from Chicago, Illinois. Originally called the Chicago-Colorado Colony, the men sold memberships in the town and with the proceeds purchased the land necessary for the town hall. The city began to flourish as an agricultural community after the building of the Colorado Central Railroad line arrived northward from Boulder in 1877. During the 1940s, Longmont began to grow beyond these original limits. During the mid-1990s, the southern edge of Longmont became the location of the first New Urbanist project in Colorado, called Prospect New Town, designed by the architects Andrés Duany and Elizabeth Plater-Zyberk.