The City of Westminster is a home rule municipality located in Adams and Jefferson counties, Colorado, United States. The city population was …The City of Westminster is a home rule municipality located in Adams and Jefferson counties, Colorado, United States. The city population was 116,317 at the 2020 United States Census with 71,240 residing in Adams County and 45,077 residing in Jefferson County. Westminster is the eighth most populous city in Colorado. The city is a part of the Denver–Aurora–Lakewood, CO Metropolitan Statistical Area and the Front Range Urban Corridor. The Westminster Municipal Center is located 9 miles north-northwest of the Colorado State Capitol in Denver.