One-drop rule

This article should be merged with  One drop theory

The "one-drop rule" in American race relations is the colloquial term for the standard that held that a person with even one drop of black blood was classified as an African-American.

The "rule" still influences the U.S. today--by de facto American color standards, a multiracial person with black heritage is considered black until they preemptively declare themselves otherwise--identifying, instead as white or Native American, for example. (This stands in contrast to Brazilian color standards, for example.)

The one-drop rule is a product of the American slavery system--it widened the pool of possible slaves, and reduced the possibility (horrifying to racist whites) that over generations African-Americans would drift into the white column.

It was codified in law in some places and held cultural sway in others. For example, as cited in the Loving v. Virginia decision, Virginia law (passing, racial purity