Still was a son of freed slaves. A prominent member of the Philadelphia Anti-Slavery Society, he was also a known leader in the movement to free other slaves, along the secret route of safe houses and areas known as the Underground Railroad. He is thought be many historians to have coined the term.

He was certainly no stranger for fighting for what he thought was right, even if it meant spending time in jail. In fact, Still arranged for 649 slaves to be free in the 1850s, in the decades before and during the Civil War. He published their stories in an 1872 book titled The Underground Rail Road: A Record of Facts, Authentic Narratives, Letters, &c. Narrating the Hardships, Hair-Breadth Escapes, and Death Struggles of the Slaves in Their Efforts for Freedom, which was displayed prominently four years later in the Philadelphia Centennial Exhibition. In the book, he writes movingly of helping his older brother, Peter, escape, meeting him for the first time in the process. Peter's story was one of several hundred that Still kept hidden in his records, for fear of being charge with violating the Fugitive Slave Law that required the return of escaped slaves and stipulated harsh punishment for those who helped them.

Still was a friend to other abolitionists, at one point providing refuge for the wife, daughter, and sons of John Brown after Brown's arrest following the attempted raid on the federal arsenal at Harpers Ferry.

Still's story was known in Philadelphia, where he also led the fight for desegregation of the city's railway cars; but the house in which he and his wife, Letitia, lived was not. Historians had long puzzled over the location of the couple's house and Underground Railroad safe house, primarily because property records from the time identified a street but not a house number. Historian Jim Duffin found the telling information in a newspaper ad.

Letitia Still was a dressmaker and advertised in 1851 for her services, including in the ad enough of a description of her house that historians today could fill in the rest of the details. The Stills lived at 625 Ronaldson Street. (It is now South Delhi Street.)

Now, the city's Historical Commission has voted unanimously to place the 19th Century house in which the Stills lived on the Register of Historic Places. Now, the house cannot be demolished or serioiusly altered. In fact, it is the second such registration associated with Still, who died in 1902 after a successful career as a businessman. He also founded an orphanage for the children of African-American Civil War veterans and was a co-founder of the magazine The Nation.