Land for sale in Gallatin County, Montana, recently totaled approximately $2 billion and around 100,000 acres. Gallatin County ranks second out of 56 counties in Big Sky Country for the total acreage of land currently advertised for sale. Bozeman had the most land for sale. From an economic perspective, government and state-level services contribute most to Gallatin County's overall GDP. Gallatin County is Montana's 24th biggest county (2,633 square miles). It's located in the Yellowstone Country Montana region of Montana.