 Lincoln was elected president on November 6 , 1860 , and the following month Booth drafted a long speech , apparently undelivered , that decried Northern abolitionism and made clear his strong support of the South and the institution of slavery . On April 12 , 1861 , the Civil War began , and eventually 11 Southern states seceded from the Union . In Booth 's native Maryland , the slaveholding portion of the population favored joining the Confederate States of America . Because the threatened secession of Maryland would leave the Federal capital of Washington , D.C. , an indefensible enclave within the Confederacy , Lincoln suspended the writ of habeas corpus and imposed martial law in Baltimore and portions of the state , ordering the imprisonment of pro @-@ secession Maryland political leaders at Ft . McHenry and the stationing of Federal troops in Baltimore . Although Maryland remained in the Union , newspaper editorials and many Marylanders , including Booth , agreed with Judge Roger B. Taney 's decision in Ex parte Merryman that Lincoln 's actions were unconstitutional . 
