Allan Pinkerton

Known now as the founder of Pinkerton’s Detective Agency, Allan Pinkerton was one of the Civil War’s most controversial figures. Before the war, he had worked as a detective in Chicago and founded his own agency, which largely focused on crimes against the railroads; it was Pinkerton who warned of a possible presidential assassination plot as Abraham Lincoln traveled to Washington for his inauguration. As the armies organized in 1861, General George McClellan brought Pinkerton in as an intelligence officer; he knew the operative from his prewar position as a railroad executive. Pinkerton rose with McClellan and became responsible for military intelligence in the eastern theater. But Pinkerton’s intelligence was completely unreliable, as he vastly overestimated the Union army’s opposition. At Antietam, McClellan hesitated to both attack and then pursue Robert E. Lee’s army because Pinkerton had convinced him that the Confederates outnumbered the Union. In fact, McClellan held a superiority of about three to one.