It is one of South Carolina’s oldest taboos: a white man of power having a secret sexual relationship with a black slave or servant.

But when news broke this weekend about the alleged liaison between the late U.S. Sen. Strom Thurmond and a 16-year-old black family servant that might have produced a daughter, it was no news at all to those who know their state history.

At the time, in 1925, Thurmond was 22 and living at home with his parents in Edgefield County. Thurmond’s father was one of the state’s most powerful and best-connected lawyers. The maid, 16-year-old Carrie Butler, was poor and unmarried.

So far, the family of the late senator isn’t saying much about the claim. But historians say, if true, it fits a well-known pattern.

“We know this kind of thing was very common — it was just not acknowledged,” said Val Littlefield, a University of South Carolina history professor who specializes in African-American Southern history.

Vernon Burton, who grew up in Ninety Six and teaches history at the University of Illinois-Urbana, agreed.

“You have a long tradition of interracial sexual relationships,” said Burton, whose book, “In My Father’s House Are Many Mansions,” chronicles the lives of blacks and whites in Edgefield between 1850 and 1880.

Both Littlefield and Burton said such relationships are almost always examples of powerful white men exploiting black female slaves and servants.

“This maid — what is she going to do?” Littlefield said.

South Carolina history is replete with documentary evidence that slave owners and powerful white men fathered children by black women.

On the eve of the Civil War, South Carolina’s great diarist, Mary Boykin Chesnut, wrote how common it was for white slave owners to have children with black slaves — and then rear the mixed-race children alongside the children of their white marriages.

“Like the patriarchs of old our men live all in one house with their wives and their concubines, and the mulattos one sees in every family exactly resemble the white children,” wrote Chesnut, the wife of slave owner James Chesnut, who was a U.S. senator and later a secessionist.

Mary Chesnut wrote that her fellow white plantation mistresses ignore their husbands’ mulatto children by pretending they “drop from the clouds.”

In the 1850s, white Edgefield County slave owner and U.S. Sen. James Henry Hammond wrote his son, Harry, a letter in which he acknowledged he had children by a slave named Louisa.

“Louisa’s first child may be mine. I think not. Her second I believe is mine ... Do not let Louisa or any of my children or possible children be the Slaves of Strangers. Slavery in the family will be their happiest earthly condition,” wrote James Hammond, as reported in Burton’s book.

In 1895, South Carolina white supremacists were embarrassed when the subject of interracial sex came up at a constitutional convention.

Some weeks into the convention, white delegates began discussing how much black blood it took to make a white person black.

The topic was of major importance because whites in 1895 not only wanted to stop blacks from voting, they also wanted to ban marriages between whites and blacks.

One white delegate, George Johnstone, argued that any degree of black blood made a person black.

But George Tillman, older brother of white supremacist and U.S. Sen. Ben Tillman, had a counterargument

George Tillman said if Johnstone’s definition were adopted, then “respectable (white) families in Aiken, Barnwell, Colleton and Orangeburg would be denied the right to intermarry among the people with whom they are now associated,” according to Francis Simkins, author of “Pitchfork Ben,” a major biography of Ben Tillman. (George Tillman was the father of Jim Tillman, the state lieutenant governor who assassinated N.G. Gonzales, the first editor of The State, in 1903.)

The discussion of how much black blood makes a person black went on so long that Robert Smalls, one of the few black delegates, proposed tongue-in-cheek that any white person who marries or cohabits with anyone who has one-eighth black blood or more should be disqualified from holding public office.

Smalls also proposed that mulatto children of such relationships be entitled to inherit property from their mothers and fathers, according to Stephen Kantrowitz in his book, “Ben Tillman and the Reconstruction of White Supremacy.”

Smalls’ point embarrassed white delegates, for in those days, it was not uncommon for whites to have secret sexual relationships with blacks, whom they claimed were not whites’ equals.

Whites ignored Smalls’ proposal.

By the end of the convention, in December 1895, white delegates figured how to deny blacks the vote. They also banned interracial marriages and defined a person as black if he had one-eighth black heritage.

Littlefield said the topic of white supremacists seeking sexual liaisons with black women has its ironies.

“The segregationist stand was to keep the races apart, but when you speak of sex, that was not happening,” she said.

Some wonder how Thurmond would have reacted to hear Essie Mae Washington-Williams make public her claim that he is her father.

“He was a master politician,” Burton said, “but I wonder how he would have handled this one.”