I'm not sure but the "Rustler's War" in Wyoming may be a reference to the Johnson County Range war of the 1890's that erupted in open warfare between the big cattlemen and the squatters to the extent that the military was sent in to secure the peace (or to protect the mercenaries hired by the cattlemen who found themselves outnumbered and out gunned. Depends on your point of view I suppose.)
Indian problems of 1890-91 may have been the "Ghost Dance" uprising of the Sioux and other tribes that resulted in the killing of Chief Sitting Bull at Standing Rock on Dec. 15 1890 and the massacre at Wounded Knee later that same month. In Robert Utley's "Frontier Regulars, The United States Army and The Indian 1866-90" on page 414: "On November 20 [1890] elements of the Second and Eighth Infantry and Ninth Cavalry, 600 strong, occupied Pine Ridge and Rosebud Agencies" This action, in response to the Ghost Dancing, "lit the fuse" for everything that followed. Hope this helps. Dale