The Marias River starts in Glacier County at the confluence of the Two Medicine River and Cut Bank Creek. It flows generally southeastward from this point and is impounded by the Tiber Dam to form Lake Elwell. About 50 miles downstream of the dam, it receives its principal tributary, the Teton River, shortly before entering the Missouri River at Loma. T he Marias River was named in 1804 by Meriwether Lewis for his cousin, Maria Wood. There are three BLM river access sites: Sullivan Bridge launch site, Pugsley Bridge Recreation Area, and Moffat Bridge Recreation Area. The Pugsley Bridge Recreation Area is located about 4.5 miles downstream of Tiber Dam. Drive across the historic cable suspension bridge to reach the river access site on the south side of the river.