Trans-Mississippi was a common name of the geographic area west of the Mississippi River during the 19th century. The term "Trans-Mississippi" was historically used to refer to any land "across the Mississippi", including Nebraska, Iowa, North Dakota, South Dakota, Kansas, Minnesota, Arkansas, Louisiana, Missouri, Texas, New Mexico, Arizona, California, Nevada, Utah, Colorado, Montana, Wyoming, Idaho, Washington and Oregon. It also included Indian Territory, Alaska, Hawaii, and other U.S. territories.