Strangely enough, the one-drop rule was not made law until the early 20th century. This was decades after the Civil War,
emancipation, and the
Reconstruction era.
The first challenges to such state laws were overruled by
Supreme Court decisions which upheld state constitutions that effectively disfranchised many. White Democratic-dominated legislatures proceeded with passing
Jim Crow laws that instituted racial segregation in public places and accommodations, and passed other restrictive voting legislation. In
Plessy v. Ferguson, the Supreme Court allowed racial segregation of public facilities, under the "separate but equal" doctrine.
Jim Crow laws reached their greatest influence during the decades from 1910 to 1930. Among them were hypodescent laws, defining as black anyone with any black ancestry, or with a very small portion of black ancestry.
[3] Tennessee adopted such a "one-drop" statute in 1910, and
Louisiana soon followed. Then
Texas and
Arkansas in 1911,
Mississippi in 1917,
North Carolina in 1923,
Virginia in 1924,
Alabama and
Georgia in 1927, and
Oklahoma in 1931. During this same period,
Florida,
Indiana,
Kentucky,
Maryland,
Missouri,
Nebraska,
North Dakota, and
Utah retained their old "blood fraction" statutes
de jure, but amended these fractions (one-sixteenth, one-thirty-second) to be equivalent to one-drop
de facto.[18]
Before 1930, individuals of visible mixed European and African ancestry were usually classed as
mulatto, or sometimes as black and sometimes as white, depending on appearance. Previously, most states had limited trying to define ancestry before "the fourth degree" (great-great-grandparents).