The Baltimore Plot was an alleged conspiracy in late February 1861 to assassinate President-elect Abraham Lincoln en route to his inauguration. Allan Pinkerton, founder of the Pinkerton National Detective Agency, played a key role by managing Lincoln's security throughout the journey. Though scholars debate whether or not the threat was real, clearly Lincoln and his advisors believed that there was a threat and took actions to ensure his safe passage through Baltimore, Maryland.
On November 6, 1860, Lincoln was elected as the 16th President of the United States, a Republican, and the first to be elected from that party. Shortly after his election, many representatives of southern states made it clear that the Confederacy's secession from the U.S. was inevitable, which greatly increased tension across the nation. A plot to assassinate Lincoln in Baltimore was alleged, and he ultimately arrived secretly in Washington, D.C. on February 23, 1861.
For the remainder of his presidency, Lincoln's many critics would hound him for the seemingly cowardly act of sneaking through Baltimore at night, in disguise, sacrificing his honor for his personal safety. However, the efforts at security may well have been prudent.
Allan Pinkerton was commissioned by the railroad to provide security for the president-elect on his journey to Washington, D.C. Maryland was a slave state with strong Southern sympathies and therefore potentially dangerous for the Republican president elect to pass through. Two months following his journey, Baltimore citizens attacked a Union Army regiment from Massachusetts as it marched through the city on its way to Washington. When Virginia seceded and joined the Confederacy, it became necessary for Lincoln to cross Maryland to reach Washington.