Grass Valley is a city in Nevada County, California, United States. As of the 2020 United States census, its population was 14,016. Situated at roughly 2,500 feet (760 m) in elevation in the western foothills of the Sierra Nevada mountain range, this northern Gold Country city is 57 miles (92 km) by car from Sacramento and 88 miles (142 km) west of Reno.