What US President was a member of KKK?

No, he was not a member of the Klan.

After the murder of civil rights worker Viola Liuzzo, Johnson went on television to announce the arrest of four Ku Klux Klansmen implicated in her death.

He angrily denounced the Klan as a "hooded society of bigots," and warned them to "return to a decent society before it's too late."

Johnson was the first President to arrest and prosecute members of the Klan since Ulysses S. Grant about 93 years earlier.