As you might expect, Atticus is no fan of the Klan. However, he also seems to be either surprisingly uninformed about the KKK (a very un-Atticus-like characteristic, since he is historically, politically and socially savvy on most subjects) or else he is deliberately trying to mislead Jem (also unlike Atticus) on the subject in order to put him at ease. The subject of the Ku Klux Klan comes up in Chapter 15, when a "gang" of people meet in Atticus' front yard. When Atticus explains that it wasn't a "gang," Jem speculates about the Klan. Atticus tells him about one appearance the KKK made many years before when they
... paraded by Mr. Sam Levy's house one night, but Sam (said) ... he'd sold 'em the very sheets on their backs. Sam made 'em so ashamed of themselves they went away."
Atticus probably sensed that Jem and Scout were worried about him, so Atticus told them
"Way back about nineteen-twenty there was a Klan... The Ku Klux's gone... It'll never come back."
How wrong Atticus proved to be. It is obvious that there must have been little or no Klan activity in the Maycomb area at the time, or Atticus would not have been so easily fooled. Again, however, he may have only been trying to calm his children by hoodwinking them with a white lie (no pun intended).