South Carolina Gov. Nikki Haley, after the massacre of nine African-Americans at a historic black church in Charleston, has called for the removal of the rebel Confederate battle flag that stands outside South Carolina's Statehouse. Days earlier authorities charged Dylann Storm Roof, 21, who is white, with murder and described the shootings as a hate crime. Roof appears in widely-seen photos holding Confederate flags, and investigators have learned that he told a friend that blacks were taking over the world and said something needed to be done for the white race. Here's a brief explanation of the Confederate battle flag, a historic but deeply divisive symbol that remains ever-present in the American South.

THE CONFEDERATE BATTLE FLAG: A LONG HISTORY

During the American Civil War in the 1860s, the rebel South's military flew several styles of Confederate battle flags — what most Americans think of as the Confederate flag. Separately, the rebel government also flew several Confederate national flags. What became the lasting symbol of the rebel South and is now known as the "Confederate Flag" or "Rebel Flag" is the rectangular version of the Confederate Army battle flag — a star-studded blue 'X' overlaying a field of red. This version was flown by various Confederate Army units, including the biggest: Gen. Robert E. Lee's Army of Northern Virginia. Many Southerners have embraced it, claiming pride in their region's heritage. It is also used to honor fallen Confederate soldiers. Parts of its design were incorporated into the state flags of South Carolina, Mississippi and Georgia — against the wishes of African-American civil rights groups. The flag has been flown over several Southern cities and has also been adopted by white supremacist groups like the Ku Klux Klan.

THE FLAG IN SOUTH CAROLINA

South Carolina was the first of 11 states to secede from the federal Union in December 1860; the first shots of the Civil War were fired at Fort Sumter in 1861. At the base of the Confederate monument at the Statehouse, the rebel flag flies atop a 30-foot (9-meter) pole. Nearby, the U.S. and South Carolina flags were recently lowered to half-staff to honor the nine black church members slain. The Confederate flag was first raised in the South Carolina House of Representatives chambers in 1938 but was not raised over the Statehouse until 1962. It was meant to commemorate the Civil War centennial but some also saw it as a show of defiance during the civil rights era. The state resolution that called for this doesn't specify when the flag will come down. Opponents of the flag have called for its removal from outside South Carolina's Statehouse, and lawmakers have taken the first steps toward taking it down after Haley's unexpected call for its removal.