In this September 21, 1923 file photo, members of the Ku Klux Klan ride horses during a parade through the streets of Tulsa, Okla. Former Sheriff Bill McCullough, who tried to stop the parade, is at foreground left. John Hartvigsen, a flag scholar, says flags' power – to unite or divide – is only as great as the significance people assign to them. (Photo by AP Photo)
