The Western United States—commonly referred to as the American West or simply The West—traditionally refers to the region comprising the westernmost states of the United States (see geographical terminology section for further discussion of these terms). Because the United States expanded westward after its founding, the meaning of the West has evolved over time. The Mississippi River is often referenced as the easternmost possible boundary of the West.
Note however that according to the U.S. Coast Guard, "The Western Rivers System consists of the Mississippi, Ohio, Missouri, Illinois, Tennessee, Cumberland, Arkansas and White Rivers and their tributaries, and certain other rivers that flow towards the Gulf of Mexico" not the Sacramento and Columbia.
The "West" had played an important part in American history; the Old West is embedded in America's folklore.
