There was a total of nearly $9 million of land for sale in San Juan County, Colorado, recently on Land.com. The total size of all San Juan County farms and ranches for sale was around 1,000 acres. San Juan County ranks 56th in the state for the total number of acres of land currently advertised for sale. Silverton had the most land for sale. San Juan County is Colorado's 60th biggest county (388 square miles). It's located in the Southwest Colorado region of Colorado.