To clarify: it wasn’t illegal to marry black people. It may have been illegal for a person of another race to marry a black person - but black people could generally still marry.

Different US states had different specificity in their miscegenation laws. Some were blanket bans, while others added explicit pairing, eg.

..the state of Oklahoma in 1908 banned marriage “between a person of African descent” and “any person not of African descent”; Louisiana in 1920 banned marriage between Native Americans and African Americans (and from 1920–1942, concubinage as well); and Maryland in 1935 banned marriages between blacks and Filipinos.