 By the time the U.S. Congress passed the Fugitive Slave Law of 1850, Pennsylvania was effectively a free state, although it would not abolish slavery completely until the ratification of the Thirteenth Amendment.It did, however, pass a personal liberty law in 1847 that made it difficult for southerners to recover any enslaved persons who made their way into Pennsylvania.Lying just north of the Mason-Dixon line, bordered by the Susquehanna River which had been a traditional route from the Chesapeake Bay watershed into the heart of what became Pennsylvania, Lancaster County was a significant destination of the Underground Railroad in the antebellum years.