[Vaquero]

Anyone can use a search engine:

President Warren G. Harding, President Woodrow Wilson, President McKinley, President Calvin Coolidge, and President Harry S. Truman.

[x]

McKinley wouldn't have been a Klan member. The old Klan was a Southern institution. The new national Klan wasn't founded until after McKinley was long dead.

Wilson sympathized with the Klan as depicted in Birth of a Nation, but he was too young for the old Klan and already in the White House when the new Klan was founded.

And I really doubt Coolidge was a Klan member.