Ian F. Haney López, White By Law: The Legal Construction of Race (New York: New York University Press, 1996), 117ff.
Naturalization and immigration laws are not, however, the only or even the most important laws that have influenced the appearance of this country’s populace. More significant may be the antimiscegenation laws, which appeared in the statutes of almost every state in the union until they were struck down by the Supreme Court in 1967. These laws purported merely to separate the races. In reality, they did much more than this: they acted to prevent intermixture between peoples of diverse origins so that morphological differences that code as race might be more neatly maintained. Antimiscegenation laws, like lynch laws more generally, sought to maintain social dominance along specifically racial lines, and at the same time, sought to maintain racial lines through social domination. As Martha Hodes argues, “racial hierarchy could be maintained primarily through the development of a rigid color line: if blacks and whites did not have children together, then racial categories could be preserved.” Cross-racial procreation erodes racial differences by producing people whose faces, skin, and hair blur presumed racial boundaries. Forestalling such intermixture is an exercise in racial domination and subordination. It is also, however, an effort to forestall racial blurring. Antimiscegenation laws  maintained the races they ostensibly merely separated by insuring the continuation of “pure” physical types on which notions of race are based in the United States.