An act relative to slaves and servants, 1817, containing a provision freeing every child born of a slave in the state who was born after July 4, 1799. This was, however, a gradual process. All such children were still bound to the master of their mother until age 28 (for males) or age 25 (for females). Every child born of a slave after this act was passed was also legally owned by the mother's master until age 21. According to the terms of the law, all slaves were to be free by 1827.
New York State Archives, NYSA_13036-78_L1817_Ch137_p2
New York State Archives. New York (State). Dept. of State. Bureau of Miscellaneous Records. Enrolled acts of the State Legislature. Series 13036-78. Laws of 1817, Chapter 137, Section 4.