Tom Horn’s enduring reputation rests on the moment in 1903 when he was hanged in Cheyenne, Wyoming, for the murder of fourteen-year-old Willie Nickell. It was, in some ways, an ironic end, for Horn was not an “outlaw” like Jesse James or Butch Cassidy or any lesser-known thief. He took nothing from his victim. He was not a murderer with any personal motive. He had very slight acquaintance with Willie Nickell or any of his family and no personal quarrel with any of them. Tom Horn was hanged because his jury believed he was an assassin, a killer-for-hire.
For most of his life, Tom Horn had been a lawman, or, at least, he had acted in the service of the law. He had been a civilian scout for the United States Army in Arizona in the 1880s. In 1890 he became an agent for the Pinkerton Detective Agency. Pinkerton’s, founded in 1850 by Allan Pinkerton and carried on by his sons William and Robert, was a private detective agency with a wide reputation. Allan Pinkerton reported on assassination plots against President Abraham Lincoln and organized spies for General George McClellan during the Civil War. William Pinkerton developed a large clientele in the U.S. West, primarily among railroads and big business interests. The Pinkerton operation worked closely with government law enforcement but preferred to use undercover agents. “Rumors persisted that detectives secretly worked on both sides of the same case, kidnapped witnesses, bribed juries, [and] commonly used violence to break strikes and coerce confessions[.]” As a result, the Pinkerton Agency’s reputation was somewhat mixed.
Horn remained less than five years with Pinkerton’s. However, he seems to have left on good terms with his employer. On April 12th, 1895, William Pinkerton recommended him to Frank M. Canton, undersheriff of Pawnee County, Oklahoma:
I am in receipt of your very full and complete letter of April 7th and note contents. As we have not got the right kind of a man for this rough work out there, I have referred the matter to Supt. McParland at Denver, sending him copy of your letter. I was greatly pleased to hear from you and did not know of your change of place. I imagine that whoever goes out on this work will find it rather difficult to do and we have not got at this office available such a man as I feel satisfied would fill the bill in every particular.
Tom Horn who used to be with our Denver office would be a good man for the place, and I will ask McParland to communicate with him and see if he cannot be got for the service and for the length of time you want him. He is not in our service now. You probably know of him. He is well acquainted all through the western country among cattle rustlers and all that class of men, and is a thorough horseman and plainsman in every sense of the word. I note particularly that you want to get Jack Treganing [sic] who excaped [sic] from the Laramie penitentiary where you sent him for life and that he is down in that country. I should be very glad indeed to hear of his capture.
I trust Mr. McParland will be able to fit you out with the right kind of a man to go down there.”
Frank Canton, who received this letter, was another man with a checkered past. When he left Texas in 1877 his name was Josiah Horner, and he was considered a bank robber, cattle rustler, and killer. In Wyoming, though, Canton became a detective for the Wyoming Stock Gowers Association and a U.S. Deputy Marshal. In 1892 Canton was in charge of a contingent of Texas men imported to Wyoming to kill suspected rustlers in an extra-legal fiasco known as the Johnson County War. Canton went on to law enforcement positions in Oklahoma and eventually became Adjutant General of the Oklahoma National Guard.
Canton apparently retained an interest in Wyoming. The escape of John Tregoning from the Wyoming Territorial Penitentiary on November 15, 1894, was, strictly speaking, no affair of an undersheriff in Oklahoma. Tregoning (going by the name of Smith) had shot and killed George Henderson (formerly known as John Powers), who was manager of the 71 Cattle Company on the Sweetwater River in Wyoming, on October 8, 1890 “in a dispute over employment.” Tregoning was believed to have returned to the Sweetwater area where he was assisted by friends. He was never recaptured.
It is not clear that Horn engaged in the search for Tregoning, but he was certainly in the Horse Creek area of southern Wyoming in the summer and fall of 1895, where, he later boasted, he had killed two men accused of stealing cattle. These murders, as much as the Nickell killing, established his reputation as an assassin.
Connections between these three ambiguous men, Tom Horn, William Pinkerton, and Frank Canton, are clearly shown by this letter, previously a part of the important Robert J. McCubbin Collection of Western historical materials. The William A. Pinkerton letter to Frank Canton about Tom Horn now resides in the collections of the American Heritage Center.
Frank Richard Prassel, The Western Peace Officer: A Legacy of Law and Order (Norman: University of Oklahoma Press, 1972), 134.
 Elnora L. Frye, Atlas of Wyoming Outlaws at the Territorial Penitentiary (Laramie: Jelm Mountain Publications, 1990), 121; Alfred James Mokler, History of Natrona County, Wyoming, 1888-1922 (Chicago: R.R. Donnelley & Sons Company), 272-275.
 Larry D. Ball, Tom Horn in Life and Legend (Norman: University of Oklahoma Press, 2014), 175-186.
- Post contributed by D. Claudia Thompson, Supervisor, American Heritage Center Arrangement and Description Department.