A former crossroads, Hills Flat became a self-sufficient community in the era of automobile travel, with utilities, several businesses, and a rapidly growing population as of 1932.[2] A referendum on annexation by Grass Valley was held in 1934, and was rejected.[3] Hills Valley residents ultimately voted to join Grass Valley in 1967.[4] Today, Hills Flat is considered a "business district" of Grass Valley,[5] best known for its large lumber yard.