Two weeks after war was declared on Spain, 85 volunteers, mostly members of the Territorial National Guard, on May 5, 1898, filled the Territory's quota as Troop A, 1st United States Volunteer Calvary, the famed "Rough Riders".
Examined and issued orders from "Camp George W. Steele" in the McKay building, 102 E. Harrison, they were sworn into federal service on the vacant lot across the street. There was much fanfare; the City of Guthrie also presented a horse to Capt. Robert B. Husten, Troop Commander. They were joined in San Antonio, TX, by units from Arizona and New Mexico Territories for brief training before fighting as dismounted Troop D at the July 1 and 2, 1898, Battle of San Juan Hill under Lt. Col. Theodore Roosevelt, who later visited veterans of the Troop in Guthrie. (See photograph).
In response to the clamor to serve, formation of the First Territorial Infantry allowed more Guardsman to enlist for the Territory quota. Guthrie's group was joined by men from Pawnee to make Co I. After mustering ceremonies on the vacant lot, the company marched under the command of Capt. Harry C. Barnes to the depot to entrain for Ft. Reno. They were joined by four other companies from Oklahoma and Indian Territories. Later, units from Arizona and New Mexico joined them for training in Kentucky and Georgia before they were mustered
out of service in 1899.