On April 1, 1837, Prigg led an assault and abduction on Morgan in York County, Pennsylvania. They took Morgan to Maryland, intending to sell her as a slave (her children, one of whom was born free in Pennsylvania, were also captured and sold). The four men involved in the abduction were arraigned under the 1826 act. Prigg pleaded not guilty and argued that he had been duly appointed by Ashmore heirs to arrest and return Morgan to their estate in Maryland. In a ruling on May 22, 1839, the Court of Quarter Sessions of York County convicted him of violation of the state law.