Born to Irish immigrants in Wickham, Canada East, on Sept. 26, 1838, Edward P. Doherty moved to New York City in 1860. When the American Civil War erupted the following April, he immediately enlisted in the Union Army as a private. Captured at the First Battle of Bull Run, Doherty managed a daring escape and by war’s end he was a first lieutenant with the 16th New York Cavalry, a unit charged with defending Washington. Ten days after President Abraham Lincoln’s assassination on Good Friday, April 14, 1865—acting on information that assassin John Wilkes Booth and accomplice David E. Herold were somewhere between the Potomac and Rappahannock rivers—Doherty was sent to apprehend them. With 25 soldiers under his command and accompanied by two detectives, Doherty had little success until a f...