Sleuths trace fate of first black male slave freed by #AbrahamLincoln. http://t.co/59ixuGXmQw pic.twitter.com/v5a5STIzJ7

— The Post and Courier (@postandcourier) July 19, 2015

MINNEAPOLIS — Researchers believe they found the grave of a man who could be considered the first black male slave freed by Abraham Lincoln, tracking his final resting place to the cemetery of a former Minnesota psychiatric hospital.

William Henry Costley was just 10 months old in 1841 when Lincoln, who was still a young lawyer, won an Illinois Supreme Court case freeing Costley’s mother from indentured servitude — a status that historians say would have been akin to enslavement for the black woman and child at that time. That was 22 years before Lincoln, as president, issued the Emancipation Proclamation, declaring slaves in rebel states not under Union control free.