The City of Louisville /ˈluːɪsvɪl/ is a Home Rule Municipality in Boulder County, Colorado, United States. The city population was 18,376 at the 2010 United States Census. Louisville began as a rough mining community in 1877, suffered through a period of extraordinary labor violence early in the 20th century, and then, when the mines closed in the 1950s, made a transition to a suburban residential community.