Johnstown is a Home Rule Municipality in Larimer and Weld counties in the U.S. state of Colorado. The population was 3,827 at the 2000 census. As of 2010 the US Census Bureau estimates the population of Johnstown at 9,887.
Johnstown is located at 40°20′10″N 104°55′13″W / 40.33611°N 104.92028°W / 40.33611; -104.92028 (40.336240, -104.920279), and stands 41 miles north of the State Capitol in Denver.
According to the United States Census Bureau, the town has a total area of 1.1 square miles (3.0 km²), all of it land.