James Davidson enlisted as a private in the Union Army in October 1861, fought in several battles, was appointed to administrative posts within the military, received "steady and rapid" promotions, and was discharged in January 1866, holding the rank of colonel. His experiences during the War became the subject of rich family lore.
He arrived in St. Paul in the autumn of 1866, studied law, was admitted to the bar, but delayed practice for five years while he edited the St. Paul Pioneer Press. He then practiced law until 1882, representing several steamboat companies; he invested in real estate and at one point owned much of the St. Paul loop; he became an entrepreneur who made and lost a fortune. He was a renowned orator for the temperance movement and a formidable debater for the Republican Party. In his last years, he moved to Chicago where he died on December 1, 1925, at age eighty-six. In his front page obituary, the Pioneer Press described him as having "held a leading part in that golden romance of Minnesota's pioneer youth, the Winning of the West."
Sometime later--probably the next year--his son wrote "The Life" of his father for a memorial service. It consisted of a series of colorful anecdotes, and concluded with the story of the Colonel's disclosure in 1925 to a Chicago newspaperman of what happened to the body of John Wilkes Booth after he was killed. Booth and his co-conspirators were cornered in a barn near Bowling Green, Virginia. The Colonel, who was commanding an infantry unit, recalled:
"That's all in the history books, but I don't have to have them read to me, because I was there. And just after the shooting of Booth, a report came to me about a group of men acting mysteriously in the middle of the night around one of the warehouses.
"I didn't have to wait long for my information. The head of the secret service in the army, Col. Baker, came to my office the very next morning and said he wanted to see me in strict privacy.
"This is what he said: . . . .