|Saint Vrain Creek|
St. Vrain Creek in Rocky Mountain National Park
|• location||Confluence of North St. Vrain and South St. Vrain|
|Confluence with South Platte|
|4,737 ft (1,444 m)|
|Basin size||993 sq mi (2,570 km2)|
St. Vrain Creek (often known locally as the St. Vrain River) is a tributary of the South Platte River, approximately 32.2 miles (51.8 km) long, in north central Colorado in the United States. It drains part of the foothills north of Boulder and the Colorado Piedmont area in the vicinity of Longmont.
Middle St. Vrain Creek rises along the continental divide, west of St. Vrain Mountain. It descends in canyon to flow along State Highway 7 and past Raymond. It joins the shorter South St. Vrain Creek about two miles below Raymond. Parts of the South St. Vrain Creek form a five mile Class 5+ kayak run during normal flows. North St. Vrain Creek rises northeast of St. Vrain Mountain near Allenspark and descends in a remote canyon to the east along U.S. Highway 36. The two branches join at Lyons, at the mouth of the canyon. East of Lyons, the combined stream flows southeast through farmland and ranch country, passing south of Hygiene and entering Longmont. It passes through the south side of Longmont where it is rimmed by a greenway trail and several parks. East of Longmont it flows generally northeast, meandering through a wide river bottom in ranch country and passing under Interstate 25 south of the intersection with State Highway 66. It joins the South Platte from the west just upstream from the ruins of Fort St. Vrain and approximately 4 miles (6.4 km) northwest of Platteville.