Before 1870, the State of New Jersey Census had only three racial or ethnic categories for residents: White, Black (free), and Black (slave), the same categories as were used in the slave states. Census enumerators tended to use black as the category for any people of color, including Indians. New Jersey passed a gradual abolition law in 1804 to end slavery; children born to slave mothers were born free. The state retained slaves born before the law in an indentured status. By a law of 1846, it reclassified them as apprentices, "apprenticed for life." The last slaves in New Jersey were not freed until 1865 and passage of the Thirteenth Amendment. In 1870, New Jersey began recording Indians (Native Americans) as a separate category in its census; 16 were identified by census enumerators that year.