It was February 1861, a few weeks before Abraham Lincoln’s inauguration, and detective Allan Pinkerton was worried: his operatives, already in Baltimore to stop any Secessionist attempts to sabotage Maryland railroads, had stumbled on a local plot to murder the president-elect. There was “decisive” information, he later wrote, that Lincoln “was to be assassinated upon his arrival and passage through Baltimore.”

The ‘Baltimore Plot,’ as it was later termed, was chillingly simple: upon arriving from Harrisburg at Calvert Street Station, Lincoln would board a carriage for Camden Street Station, over a mile away, where a train was waiting to take him to Washington. According to Pinkerton, the plotters would incite a small riot as Lincoln traveled between trains, and attack the president-elect during the chaos.

Lincoln, as the imminent head of a nation tearing itself in half, received threats in the mail on what must have been a numbing basis; meeting with Pinkerton in Philadelphia, he was resolute in sticking to his plans, even as the detective suggested he slip through Baltimore thirty-six hours ahead of schedule. “He had engagements with the people, he said, to raise a flag over Independence Hall in the morning, and to exhibit himself at Harrisburg in the afternoon,” recalled Ward Lamon, Lincoln’s former law partner and self-appointed bodyguard.

Despite his cool demeanor, Lincoln also recognized how serious Pinkerton was, and ultimately decided to place himself in the detective’s hands — provided he could still keep his appointment at Independence Hall.

The Plum Assignment

On the night of February 22, 1861, Lincoln arrived at the train depot in Philadelphia dressed in a loose overcoat and black slouch hat, stooping against Pinkerton to disguise his great height. Great pains had been taken to keep his movements secret. Lamon, following close behind, had offered his friend a revolver and Bowie knife, much to Pinkerton’s dismay. “I would not for the world have it said that Mr. Lincoln had to enter the National Capitol Armed,” the detective later wrote.

They boarded a special train five minutes before departure, and rumbled off into the dark. Pinkerton had arranged for agents waiting along the route to signal the way was safe as the train passed. Lincoln stayed in his specially pointed car, quietly cracking jokes to relieve some of the tension. By three-thirty in the morning they were in Baltimore, where Pinkerton was given yet another all-clear signal. Three hours later, the party was in sight of the Capitol dome. From Washington, Pinkerton wired coded messages to his contacts, including his chief clerk, George H. Bangs: “Plums has Nuts — arri’d at Barley — all right.”

The crowd waiting as the president’s scheduled train pulled into Baltimore that afternoon were doubtlessly surprised to only see Mrs. Lincoln, her family, and Lincoln’s private secretary. Newspapers blasted what they perceived as the president’s cowardly entering of Washington, but the ruse had worked, and Pinkerton now had a vital inside line to the administration.

Both contemporaries and historians have doubted the veracity of the plot. And Isaac N. Arnold, a friend of Lincoln’s, recorded the president as saying, “I did not then, nor do I now believe I should have been assassinated had I gone through Baltimore.” Nonetheless, there was danger in the air during those tumultuous days — and what better person to guide a president-elect safely through it than 19th century America’s most famous private eye?