The Knights of Mary Phagan were a division of the Ku Klux Klan who became infamous for their involvement in the lynching of Leo Frank on October 16, 1915 as well as popularizing the now common Klan practice of cross burning.
They were inspired by the film Birth Of A Nation and following the lynching many members of this group were brought into the second official revival of the Ku Klux Klan by then Grand Wizard, William Joseph Simmons