[1][2] She also had a role in uncovering the 1861 Baltimore Plot against President-elect Abraham Lincoln,[3][4] recruiting female agents for the Pinkerton Agency,[5] and conducting intelligence work for the Union during the American Civil War.

[6] Very little is known about Kate Warne prior to her working for Allan Pinkerton, except that she was born in Erin, Chemung County, New York and was a widow by age 23.

[7] An obituary following her death described her parents as "honest and industrious people" and stated that they were poor, resulting in her taking over many of the household duties.

[8] Pinkerton, in his book The Spy of the Rebellion (1883), described her as a commanding person, with "clear cut, expressive features" and called her a "slender, brown-haired woman, graceful in her movements and self-possessed."

In 1858, Warne was involved in the case of Adams Express Company embezzlements, where she was successfully able to bring herself into the confidence of the wife of the prime suspect, Mr. Maroney.

In 1860, Allan Pinkerton put Warne in charge of his new Female Detective Bureau, which was based in Chicago, Illinois.

As the investigation proceeded, Pinkerton became aware that the activity in Maryland did not just end with the railroad; it also included the president-elect, Abraham Lincoln.

[20] The president-elect, Abraham Lincoln, was traveling from his home in Springfield, Illinois, to the capital via a train tour that was to stop at notable cities along the way.

His published program showed that Lincoln's last leg of the journey was from Harrisburg, Pennsylvania, to Washington, D.C. Due to the configuration of the rail system, all southbound trains required a transfer to be made in Baltimore.

It was further alleged that a small steamship had been chartered, sitting in a nearby river, on which the murderers would flee, and travel immediately to the state of Virginia.

[21] After seeing the pieces of the plot coming together, Pinkerton directed Kate Warne to take the 5:10 evening train to New York City on the morning of February 18.

Once there, she was to set up a meeting with Norman B. Judd and give him a letter from Pinkerton outlining the known details of the assassination attempt.

His agenda included: giving three speeches, raising of the American flag at Independence Hall, and attending a high-profile dinner.

At the station, Warne entered the sleeping car through the rear along with Pinkerton, Ward Hill Lamon, and a still-disguised Lincoln.

The disguises provided by Warne that night enabled Lincoln to make it through Baltimore without recognition and take his seat in the White House.

Warne was key in the foiled Baltimore assassination plot – not only did she help uncover its details, but she also carried out most of the arrangements to smuggle Lincoln into Washington.

[28][29][30] After the quelled assassination attempt on president-elect Abraham Lincoln, Kate Warne continued to travel with Allan Pinkerton as his Female Superintendent of Detectives.

Robert Pinkerton often argued with Warne over expenses turned over to the agency, but her relationship with Allan continued for years.

Pinkerton determined that Gordon was fetching money for a friend or someone who frequented the bank when he was struck on the head behind the ear with a hammer with intent to murder any witnesses of the robbery.

Warne took the name Lucille and assumed the role of a fortune teller to lure information out of the suspected murderer's confidants.

[34][42] Erin Allen, who managed the Library of Congress blog, called Warne an "intriguing figure" and speculated that little documentation remains "because she was a good spy.

An obituary in the Democratic Enquirer of McArthur, Ohio on March 19, 1868, described her as "marked woman amongst her sex" who had "great mental power" and was "an excellent judge of character" and called her the "best female detective in America, if not in the world.

"[34] Until 2013, a webcomic entitled Kate Warne, Pinkerton Detective, by Lauren R. Silberman, ran, and was described as "delightful" and "homespun".

[55][56] In August 2021, Amazon Studios acquired the distribution rights to an upcoming film produced by Seven Bucks Productions starring Emily Blunt as Warne.