That Abraham Lincoln was the first American president to fall to the hand of a political assassin is one of the simple facts that almost everyone can recognize. That the blow which killed him in 1865 was not the first attempt on his life is less well known. Even as Lincoln was en route to Washington in February, 1861, he was solemnly briefed in Philadelphia by the pioneering Chicago detective, Allan Pinkerton, that “certain parties” in Baltimore had arranged an ambush there to murder him “whilst passing through Baltimore.” The report gained more traction with Lincoln when Pinkerton was followed by another visitor – Frederick Seward, the son of Lincoln’s nominee for Secretary of State, New York Senator William Henry Seward – with an almost-identical warning about a Baltimore plot...
 Pinkerton’s Report (February 21, 1861), in Herndon’s Informants: Letters, Interviews, and Statements about Abraham Lincoln, eds. Rodney O. Davis & Douglas L. Wilson (Urbana: University of Illinois Press, 1998), 312.
Guelzo, Allen C.
"The Lincoln Conspiracy: The Secret Plot to Kill America’s 16th President—and Why It Failed,"
Civil War Book Review: Vol. 22
Available at: https://digitalcommons.lsu.edu/cwbr/vol22/iss2/12