Pronounced muh-RYE-uss, the Marias River was named by Meriweather Lewis of the Lewis and Clark Expedition after his cousin Maria Wood. When they first discovered the river on their westward journey in 1805, they weren't at first certain whether it was the main branch of the Missouri River. Lewis explored the river, but the discovery of the Great Falls of the Missouri, at the site of the present city of Great Falls, convinced the expedition that the real Missouri was the southern branch.
The Marias River is formed by the confluence of several streams just south of Cut Bank.
