William Still was born in Burlington County, New Jersey. His father, Levin Steel, had been enslaved, purchased his own freedom, and changed his name to Still to protect his wife, Sidney. Mrs. Still had tried to escape once before she succeeded but could only bring two of her children with her. William Still had little formal education but studied whenever he could. In 1844, William moved to Philadelphia.
In 1847, he found a job as a clerk and janitor for the Pennsylvania Society for the Abolition of Slavery. He soon began aiding fugitive slaves, often sheltering them until they could find their way farther north. One fugitive was his older brother, Peter, who had been left behind when his mother escaped forty years earlier. These experiences led William to save careful records about the people he helped. Meanwhile, Still purchased real estate, opened a store selling stoves, and later founded a successful coal business.
Before the Civil War, Still had destroyed many of his records about aiding fugitives, because he feared they would be used to prosecute people. After the war, his children persuaded him to write the story of his exploits and the people he helped. Still's book, The Underground Railroad (1872), is one of the most important historical records we have. Although Still recognized the many contributions of white abolitionists, he portrayed the fugitives as courageous individuals who struggled for their own freedom. Still proudly exhibited his book at the Philadelphia Centennial Exposition in 1876.
As a Station Master for Philadelphia Still had dealings with Sydney H. Gay and Louis Napoleon as individuals moved north through the railroad, coming to New York and through Staten Island, and some of his records overlap with Gay's Record of Fugitives.