The Sangre de Cristo Range, the largest and most northerly subrange of the Sangre de Cristo Mountains, runs directly along the east side of the Rio Grande Rift, extending southeast from Poncha Pass for about 75 miles (120 km) through south-central Colorado to La Veta Pass, approximately 20 miles (32 km) west of Walsenburg. They form a high ridge separating the San Luis Valley on the west from the watershed of the Arkansas River on the east.