Boulder is a city in Boulder County located at the base of the Rocky Mountains, approximately 30 miles northwest of Denver. The city began as a supply town during the Colorado Gold Rush and later developed into a center for higher education, scientific research, and technology. The University of Colorado Boulder and several federal research laboratories are located in the city. The Flatirons form a prominent geographic feature along Boulder’s western edge. Pearl Street Mall is a pedestrian district with restaurants, shops, galleries, and public spaces. Boulder also maintains an extensive open-space system with hundreds of miles of trails. Housing includes single-family homes, townhomes, condominiums, and apartments, with properties ranging from historic residences to newer construction.