Grass Valley is a census-designated place in northeastern Pershing County, Nevada, United States. As of the 2010 census the population was 1,161. Grass Valley is located 10 miles south of Winnemucca. The CDP is named after the valley in which it lies, a 5-mile-wide basin between the Sonoma Range to the east and the East Range to the west. Nevada …Grass Valley is a census-designated place in northeastern Pershing County, Nevada, United States. As of the 2010 census the population was 1,161. Grass Valley is located 10 miles south of Winnemucca. The CDP is named after the valley in which it lies, a 5-mile-wide basin between the Sonoma Range to the east and the East Range to the west. Nevada State Route 294 runs from Grass Valley into Winnemucca.