West of the Mississippi The series of conflicts in the western United States between Indians, American settlers, and the United States Army are generally known as the Indian Wars. Many of these conflicts occurred during and after the Civil War until the closing of the frontier in about 1890. However, regions of the West that were settled before the Civil War saw significant conflicts prior to 1860, such as Texas, New Mexico, Utah, Oregon, California, and Washington state.

Various statistics have been developed concerning the devastation of these wars on the peoples involved. Gregory Michno used records dealing with figures "as a direct result of" engagements and concluded that "of the 21,586 total casualties tabulated in this survey, military personnel and civilians accounted for 6,596 (31%), while Indian casualties totaled about 14,990 (69%)" for the period of 1850–90. However, Michno says that he "used the army's estimates in almost every case" and "the number of casualties in this study are inherently biased toward army estimations". His work includes almost nothing on "Indian war parties", and he states that "army records are often incomplete".