Of particular influence to Twain at the time of his writing of Pudd'nhead Wilson, was the Supreme Court case of Plessy v. Ferguson.  While the case was not heard by the Supreme Court until 1896,--two years after the publication of this novel--it had been pending since 1893.  The case surrounds Homer Plessy boarding a train marked for whites only.  Plessy, black by law but white in appearance, boarded the train and then announced that he was in fact black, leading to his removal from the train.  His case centers on the idea of the "one-drop rule," which determined that a man/woman was black if they had one drop of negro blood.  The result of this case was the "separate but equal doctrine," which asserted that separate facilities for whites and black were legal as long as they were equal.  The Court's ruling stood until 1954, when Brown v. Board of Education of Topeka, Kansas was heard before the court.  It was not until well into the Civil Rights Movement of the late 50s and early 60s that segregated facilities actually began to disappear.

Homer Plessy deliberately tested this rule to test the state of Louisiana's 1890 railroad law.

From: Eric J. Sundquist, "Mark Twain and Homer Plessy"

Susan Gillman notes that "Twain's novel implicitly reminds readers that racial codes regulating miscegenation and classifying mixed-race offspring did not disappear after Emancipation, but instead were reenacted or reaffirmed, with even more rigorous definitions of whiteness, during the nineties when antiblack repression took multiple forms, legal and extralegal" (87-88).  Twain's novel hints at both the racism of slavery as well as the racism of the world contemporary to his writing.

Fractions of blood and the one-drop rule

In Latin America and the British West Indies, specific names were givn to specific levels of miscegenation. Mulatto, or 1/2 white; sambo, or 1/4 white; quadroon, 3/4 white; mestizo, 7/8 white.  Twain plays with these ridiculous levels of "whiteness" by making Roxy 1/16 black or 15/16ths white.

The "one-drop rule" refers to the notion that it only takes one-drop of black blood to make a man black.  For more information on this rule, see the links section.