What river, formed in western Montana, empties into the Mississippi just north of St. Louis?

The river that originates in western Montana and flows into the Mississippi River just north of St. Louis is the Missouri River. It is one of the longest rivers in North America, spanning approximately 2,341 miles. The Missouri River plays a significant role in the geography and history of the United States, serving as a major waterway for exploration, trade, and transportation.

This river begins in the Rocky Mountains of Montana and meanders through several states, including North Dakota, South Dakota, Nebraska, and Iowa, before it finally joins the Mississippi River near St. Louis, Missouri. The Missouri River has numerous tributaries and has historically been vital for the agricultural and economic development of the plains and Midwest regions.

The other rivers listed – the Colorado, Snake, and Ohio – originate in different locations and flow into separate bodies of water, making them unrelated to the geography in question regarding their connection to the Mississippi River. The Ohio River, for example, is a significant tributary of the Mississippi but flows from further east rather than the western region where the Missouri is formed. Thus, the Missouri River is the correct answer associating with the geographic query presented.