1806 Certificate of Abandonment, Piscataway Township, New Jersey. This document freed a slave owner from any obligations to the child born to her slave, 1806. 1808 "Manumission of Abigal," a manuscript document freeing the slave woman Abigal in Piscataway, Middlesex County, 1808. 1828 The Manumission of Ann and Rufus Johnson. Ann and Rufus Johnson were 14 and 15 years old respectively when New Jersey enacted gradual manumission in 1804.