Maybe it was love. Or patriotism. Or boredom back home in Minnesota.

There's plenty we don't know about Frances Clayton — a St. Paul wife who dressed up as a man in 1861 and marched off to the Civil War to fight alongside her husband, Elmer Clayton.

Historians say she was among nearly 400 women who cross-dressed their way into battle during the War Between the States. She added the phony name Jack Williams to her disguise, according to one rather reputable source: the Library of Congress.

The national library's website includes an 1865 photograph of Clayton (tinyurl.com/FrancesClayton) fingering a sword in the Boston photography studio of Samuel Masury.

Another of Masury's albumen silver prints from a glass negative survives on the website of Manhattan's Metropolitan Museum of Art (tinyurl.com/FrancesClayton2) saying its photo shows how Clayton "suggestively holds the handle of a cavalry sword between her crossed legs."

Soldiers collected small postcards of that image after the war, according the Met's website. Newspaper accounts from the time offer varying details of Clayton's 22-month service with a heavy artillery company and a cavalry unit out of Missouri. The St. Paul Daily Press said she fought in the Tennessee battles of Shiloh and Murfreesboro.

Library of Congress, Star Tribune
An estimated 400 women disguised themselves as soldiers during the war. These images from the Minnesota History Center’s exhibit show Frances Clayton, who fought at the battle of Shiloh and Murfreesboro, where her husband was killed.

A Cleveland Plain Dealer newspaper reporter, after Clayton's discharge in 1863, "gained a few facts from Mrs. Clayton … in regards to her romantic history."

She told the reporter she lived in St. Paul with her husband before moving to St. Louis to enlist — "donning a suit of soldier's attire, passing herself off as her husband's brother, and escaping detection."

Her husband was shot and killed "just five paces in front of her," the Grand Rapids (Mich.) Eagle reported. "She charged over his body … driving the rebels with the bayonet."

Newspaper accounts differ on where Elmer died in Tennessee — Shiloh or Stones River. His wife, meanwhile, was wounded three times — once through the wrist and twice to the hip. One newspaper said that final hip injury landed her in a field hospital, "where her sex was, of course, discovered."

Other accounts had her breaking the news to Gen. William Rosecrans, who called her "a darned little scoundrel … and a darned good little fellow."

Clayton's postwar life has been largely lost in the fog of history. She said Confederate guerrillas attacked her train between Nashville and Louisville, stealing her money and papers.

She told the Cleveland reporter she was anxious to go to St. Paul, but was broke. An Ohio woman raised "a sum necessary."

A U.S. Census log recorded in 1885 lists a Frances Clayton living near Austin, Minn., in Mower County. She was 42 in 1885, which would mean she was born in 1843 and about 20 if she was the same Frances Clayton who fought in Tennessee. That census report says Clayton was a New York native, while other sources say she was born in Illinois in the 1830s.

Either way, she deftly played the role of a man.

"While in the army, to better conceal her sex, she learned to drink, smoke, chew and swear with the best, or worst, of the soldiers," the Michigan newspaper reported in November 1863. "She is a very tall, masculine looking woman, bronzed by exposure to the weather."

The paper said her manly walking stride and "erect and soldierly carriage" attracted attention. The reporter said that when some soldiers began following her "rather too familiarly," Clayton drew a revolver to scatter the crowd.

"She took up all the manly vices," according to a 2003 book, "They Fought Like Demons," which features a photo of Clayton on the cover. "She was especially fond of cigars. She even gambled, and a fellow soldier declared that he had played poker with her on a number of occasions."

After the war, Clayton drifted amid Missouri, Minnesota, Michigan and Illinois — hoping to collect the money owed for her service and her husband's. The last reports said she was headed to Washington, D.C.

"Her camp life experience of nearly two years seems to have pretty effectually destroyed her womanly instincts," the Cleveland newspaper reported. "She wears a sort of mongrel attire — half male and half female."

Despite the dearth of details about her later years, including when and where she died, Clayton lives on in both online videos and the stage. The Minnesota Historical Society produced a five-minute video (tinyurl.com/MNFrances) that tells the story of several women who played critical roles in the Civil War, including Clayton.

Local playwright Beth Gilleland's 1996 "Civil Ceremony" focused on Clayton and was most recently staged at Blake High School last fall.

(Caption: Frances Clayton about 1864. Courtesy Library of Congress.) A report from the “St. Paul Daily Press” described Frances Clayton who was so determined to fight in the war alongside her husband, she dressed up in a man’s uniform and mustered in Co. A 13th Missouri Cavalry. According to the newspaper she fought at the battle of Shiloh and Murfreesboro where her husband was killed in action. An estimated 400 women disguised themselves as soldiers during the war.

When that Cleveland reporter interviewed her in 1863, he said Clayton eyed him closely and asked why he hadn't joined the Army. When the reporter said he had indeed fought at Bull Run, "strange to say, the woman grasped his hand at this avowal and gave it a generous shake!"

"She is a true heroine," the reporter concluded in 1863, "and really deserves a paragraph in the history of this 'cruel war.' "

Curt Brown's tales about Minnesota's history appear each Sunday. Readers can send him ideas and suggestions at mnhistory@startribune.com. A collection of his columns is available as the e-book "Frozen in History" at startribune.com/ebooks.