Laws dating from 17th-century colonial America defined children of African slave mothers as taking the status of their mothers, and born into slavery regardless of the race or status of the father, under partus sequitur ventrem. The association of slavery with a "race" led to slavery as a racial caste. But, most families of free people of color formed in Virginia before the American Revolution were the descendants of unions between white women and African men, who frequently worked and lived together in the looser conditions of the early colonial period. While interracial marriage was later prohibited, white men frequently took sexual advantage of slave women, and numerous generations of multiracial children were born. By the late 1800s it had become common among African Americans to use passing to gain educational opportunities as did the first African-American graduate of Vassar College Anita Florence Hemmings. Some 19th-century categorization schemes defined people by proportion of African ancestry: a person whose parents were black and white was classified as mulatto, with one black grandparent and three white as quadroon, and with one black great-grandparent and the remainder white as octoroon. The latter categories remained within an overall black or colored category, but before the Civil War, in Virginia and some other states, a person of one-eighth or less black ancestry was legally white. Some members of these categories passed temporarily or permanently as white.