Allan Pinkerton. 1884. Library of Congress Prints and Photographs Division.

Walking into the Chicago office of Allan Pinkerton’s detective agency one afternoon in 1856 was a woman of medium height, “slender, graceful in her movements, and perfectly self-possessed in her manner.” Claiming to be a widow, aged 23, Kate Warne was looking for a job, and not as a secretary. One could imagine Pinkerton’s surprise at such a request – women just weren’t employed for such things. Needless to say, Pinkerton decided to give Warne a chance. Perhaps it was her dark blue eyes “filled with fire” and the quiet strength and compassion she radiated that tipped the scales in her favor.

Hiring Warne would turn out to be one of the best decisions Pinkerton ever made. She became the first female detective in the United States and would become the superintendent of the female bureau of the Chicago office.

“In my service you will serve your country better than on the field. I have several female operatives. If you agree to come aboard you will go in training with the head of my female detectives, Kate Warne. She has never let me down,” Pinkerton once said.

Warne offered a skill set that Pinkerton’s male agents didn’t have – the ability to gain the confidence and friendship of other women for the purpose of gaining valuable information related the agency’s criminal cases.

According to author Daniel Stashower, Warne proved herself to be fearless and versatile. In one investigation, she posed as a fortune-teller to entice secrets from a suspect. In another, she made friends with the wife of a suspected murderer.

Warne played an integral part in several high-profile cases. Early on in her career, she was brought on board the case of the Adams Express Company – the detective agency was investigating the theft of several thousand dollars from the railroad company. Pinkerton had a hunch the money was stolen by a man named Nathan Maroney, the manager of the Adams Express office in Montgomery, Ala., and the last person to have possession of the locked pouch the money had been kept in. Pinkerton sent Warne in to befriend Maroney’s wife in hopes that she would divulge the truth of her husband’s actions. And that she did, taking Warne to the location where the money was hidden and thus solidifying the evidence and case against Maroney.

Pinkerton wrote, “The victory was complete, but her [Warne] faculties had been strained to the utmost in accomplishing it, and she felt completely exhausted. She had the proud satisfaction of knowing that to a woman belonged the honors of the day.”

Warne would prove herself yet again valuable in what was probably the defining case of her career. In 1861, Pinkerton foiled an attempt to assassinate newly elected President Abraham Lincoln while on a whistle-stop train trip to Washington, D.C., for his inauguration. While investigating robberies on the Philadelphia, Wilmington and Baltimore Railroad, Pinkerton uncovered the plot. He sent Warne to Baltimore as a spy to infiltrate the southern sympathizers. Posing as a Mrs. Barley, a visitor from Alabama, Warne’s job was to “cultivate the wives and daughters of suspected plotters.” The attempt on the president-elect’s life would be made while he was passing through the city.

Adalbert John Volck. Passage through Baltimore from V. Blada’s “War Sketches.” Baltimore: 1864. Rare Book and Special Collections Division, Library of Congress

“Mrs. Warne was eminently fitted for this task. Of rather a commanding person, with clear-cut, expressive features, and with an ease of manner that was quite captivating at times, she was calculated to make a favorable impression at once,” Pinkerton wrote in his book, “The Spy of the Rebellion.” “She was of Northern birth, but in order to vouch for her Southern opinions, she represented herself as from Montgomery, Alabama, a locality with which she was perfectly familiar, from her connection with the detection of the robbery of the Adams Express Company, at that place.

“Mrs. Warne displayed upon her breast, as did many of the ladies of Baltimore, the black and white cockade, which had been temporarily adopted as the emblem of secession, and many hints were dropped in her presence which found their way to my ears, and were of great benefit to me.”

Warne’s involvement went even further. Not only did she courier messages to Lincoln’s party, but she also helped smuggle the president himself onto a train that would ultimately pass through Baltimore with him undetected.

Stashower’s book “The Hour of Peril” chronicles the case, including Warne’s involvement. For his book, Stashower conducted research at the Library, using the Records of the Pinkerton’s National Dectective Agency and the papers of Abraham Lincoln and John G. Nicolay.

In this video, Stashower discusses his book and Warne’s involvement in foiling the “Baltimore Plot.”

Warne continued on in Pinkerton’s employ until 1868, when she fell ill and died. She is buried in the Pinkerton family plot in Graceland Cemetery in Chicago.

The Library’s Pinterkton Detective Agency collection doesn’t contain many references to Warne. Of particular note is a pamphlet, written by Pinkerton, of the events in 1861. It was written in response to a published letter by John A. Kennedy, who claimed, along with his detective force, the responsibility of discovering the plot. In the pamphlet are references to Warne corroborating her involvement in the Baltimore plot.

Most of the Pinkerton’s Chicago office files were destroyed in a fire in 1871, so beyond Pinkerton’s published writings, little more is known of the female detective. Warne was certainly an intriguing figure, and perhaps little documentation exists because she was a good spy!

This obituary of sorts in the March 19, 1868, issue of the Democratic Enquirer (Ohio), recounts news of Warne’s exploits while at the Pinkerton agency.

“Up to the time of her death, her whole life had been devoted to the service into which she had entered in her younger years. She was undoubtedly the best female detective in America, if not the world.”

Sources: Daniel Stashower, “The Hour of Peril: The Secret Plot to Murder Lincoln Before the Civil War” (St. Martin’s Press, 2013); www.pinkerton.com; Pinkerton’s National Detective Agency records, 1853-1999, Manuscript Division, Library of Congress