The Proposed Constitutional Amendment
In 1912, Congressman Seaborn Roddenberry of Georgia proposed an amendment to the Constitution of the United States that would have prohibited interracial marriage:
"That intermarriage between negroes or persons of color and Caucasians or any other character of persons within the United States or any territory under their jurisdiction, is forever prohibited; and the term 'negro or person of color,' as here employed, shall be held to mean any and all persons of African descent or having any trace of African or negro blood."
Congressional Record, 62nd Congress, 3rd session, Dec. 11, 1912. Vol 49, p. 502
This amendment was never passed. However, it is significant that such racism was present at such a high level of government.
Note that the proposed amendment defines "negro or person of color" as a person with "any trace of African or negro blood." This logic was commonly referred to as the "one drop rule," which applied to anyone with an African ancestor anywhere in their family tree.
Fourteenth Amendment (1868):
This amendment to the U.S. Constitution was meant to guarantee equal protection under the law. However, interpreted this amendment differently at various points in history. Before Brown v. Board of Education, segregation was considered constitutional according to the "separate but equal" doctrine. Before Loving v. Virginia, bans on interracial relationships were considered constitutional as long as both parties were given the same punishment.
This is the original text from Section 1 of the 14th Amendment:
Section. 1. All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.