By the time Maryland got around to ending slavery, 152 years ago next week, the Confederacy was within months of collapsing, black people in the District of Columbia had been free more than two years and President Lincoln had declared emancipation in the South more than a year and a half earlier. What took Maryland so long? Historian C.R. Gibbs explains how Maryland’s elites split over what course to follow, how heroic fighting by black soldiers in the Union army affected public opinion, and, once a new state constitution to abolish slavery was put to referendum, how close the vote was.