St. Vrain Mill is a stone, water-powered, vertical gristmill in the Mora Valley that was one of several mills supplying flour and meal to nearby Fort Union in the mid-1800s. Ceran St. Vrain built it in 1864 after his wood mill in Taos burned, and he operated it until his death in 1870. The mill continued to supply flour and grain to Mora Valley residents until 1933, and after years of neglect, rehabilitation began in 2015.