The Atlanta chapter of the National Association for the Advancement of Colored People (NAACP) is now demanding that Stone Mountain’s slate be wiped clean -- literally. Calling the image “a glorification of white supremacy,” the group wants it scraped from the mountain’s face.

It’s no secret that Confederate leaders during the Civil War explicitly defined their cause as a defense of slavery and white supremacy. A towering carving of the Confederacy’s most powerful political and military leaders would, therefore, seem a clear glorification of that cause. And the same could be said for other Confederate monuments across the country.

But many staunch defenders of the Confederate battle flag argue it’s an important symbol of Southern heritage and culture, and commemorates the hundreds of thousands of soldiers who valiantly fought and died for “the Lost Cause.”

Stone Mountain’s role in memorializing this cause, however, is a bit more nuanced. Embedded in this mountain are two stories, only one of which is captured in the bas-relief.

Lesser known is that Stone Mountain is the symbolic birthplace of the modern Ku Klux Klan. The original Klan, founded in 1865, had been largely stamped out by the mid-1870s after a period of aggressive federal intervention during Reconstruction. In 1915, William J. Simmons, a former Methodist preacher, launched a campaign to reestablish the group. Purportedly inspired by the film "The Birth of a Nation," a blatantly racist “historical romance” glorifying the original Klan, Simmons led a small group up Stone Mountain one November night in advance of the film’s Atlanta debut. At the summit, they set a cross ablaze.

The reestablished Klan's white supremacist ideology -- primarily targeting blacks, but also Jews, Catholics and foreigners -- struck a chord in the South, and the group rapidly expanded. By the mid-1920s, national membership was estimated in the millions, including sizable pockets in some northern states. Minority communities found themselves increasingly terrorized by vigilante gangs of hooded, white-robed men.

This historical footnote is, not surprisingly, omitted from the description on Stone Mountain's corporate website. But the two histories are inextricably linked.

At the time of the Klan’s resurgence, Stone Mountain was owned by aa quarry operator named Samuel Venable. A fan of "The Birth of a Nation," Venable accompanied Simmons on that November night and became an active member of the group, hosting regular Klan ceremonies on the mountain.

Venable later leased a portion of the land to a Georgia chapter of the United Daughters of the Confederacy who set out to build a memorial to the Lost Cause. Gutzon Borglum, a Danish-American sculptor and Klan member designed the massive bas-release, proclaiming it would be the “the greatest monument ever built,” comparable to the Egyptian pyramids. Helen Plane, head of the local UDOC chapter, went to great lengths to persuade Borglum to include the Klan in the memorial. She wrote:

“I feel it is due to the Klan which saved us from Negro domination and carpetbag rule, that it be immortalized on Stone Mountain. Why not represent a small group of them in their nightly uniform approaching in the distance?”

There was strong support for the idea, and it would may have come to pass had the project not run out of funding. Borglum left in a huff, and the effort languished for decades, with only the carving of Lee’s head finished. (Borglum later established his reputation with another monumental project: Mount Rushmore.)

The spark that finally spurred Stone Mountain’s completion came from an unexpected place: the Civil Rights Movement.

In the run-up to the Supreme Court’s 1954 Brown v. Board of Education decision prohibiting racial segregation, pro-segregationists breathed new life into Confederate symbolism.

Strom Thurmond’s breakaway Dixiecrats displayed the battle flag prominently at their convention in 1948. By 1951, a newspaper in Gastonia, North Carolina, was commenting on “the rash of Confederate flags which have broken out on Southern windshields, ties, and other decorative spots.” The same year, The Nation reported that “nearly one car out of ten now flies the Stars and Bars [sic] defiantly from its radio aerial.”

Soon, the flag made its way into official symbolism. In 1956, Georgia adopted a new state flag with a design incorporating the Confederate flag. And in 1961, South Carolina raised the Confederate flag over its statehouse to ostensibly commemorate the centennial of the Civil War’s start. Alabama followed suit in 1963, after Gov. George Wallace ordered it raised in advance of a visit by U.S. Attorney General Robert Kennedy to address Wallace's resistance to integration of the University of Alabama.

By 1958, the state of Georgia had bought Stone Mountain and pushed ahead with plans for a revised bas-relief design featuring Lee, Jackson, and Davis, sans Klansmen. Work surged forward, and piece by piece the image of the Confederacy was hammered into stone. As the Civil Rights Movement roiled across the country, workers used thermo-jet torches to finalize the details of Jefferson Davis’ eyebrows.

In the eyes of state leaders, writes historian Grace Hale, “the carving would demonstrate to the rest of the nation that 'progress' meant not black rights but the maintenance of white supremacy.”

After decades of work, the monument was formally dedicated in 1970. Republican Vice President Spiro Agnew, flanked by segregationist Democrats, addressed thousands of attendees who came to witness the unveiling.

Today, millions of visitors each year flock to Stone Mountain, now Georgia’s most visited attraction. The park offers hiking, fishing, golf and rides. There's even a laser light show.

It also offers visitors a cunningly crafted view of the past, eulogizing the leaders of the Confederacy and celebrating their cause as valiant and noble.

It's a mythology that's seeped more deeply into American culture than many realize.

This is evident in some history textbooks claiming that thousands of black Southerners fought for the Confederacy. It's evident in Tennessee’s 2015 commemoration of Nathan Bedford Forrest Day, whose namesake, a Confederate Army general, was also a former slave trader. It's evident in the vitriolic manifesto of alleged Charleston shooter Dylann Roof, who claims to have read hundreds of slave narratives, “almost all of [which] were positive.” It's even evident in Calhoun Street where the church shooting happened: John C. Calhoun, Andrew Jackson's vice president, was perhaps best known for his vehement defense of slavery as a positive good.

Roof didn't have go digging through the archives to assemble the white supremacist worldview for motivated. It was all around him, continually repurposed and made visible in monuments and flags.

Ironically, it’s the relative restraint of Stone Mountain’s design that’s made it such an effective vector for this line of thinking. While the Klan’s decades of terrorism ultimately relegated it to the proverbial shadows of white America, Stone Mountain never faced such a backlash. One hundred years after the monument was first imagined, most Americans have no idea how closely its history is entangled with the birth of the 20th century Ku Klux Klan.

As a result, Stone Mountain endures, its message carved into the American landscape.