Whatever Happened to The Thirteen Club?

One bit of Friday the 13th trivia I came across that intrigued me the most was the Thirteen Club.

A People article that talked about the club explained:

“[I]ts stated mission was to improve the standing of the holiday and also flout all manner of superstitions. At its first meeting, all 13 members walked under ladders into a room filled with spilled salt. The group’s ranks swelled to 400 eventually, taking in five U.S. Presidents: Chester Arthur, Grover Cleveland, Benjamin Harrison, William McKinley and Theodore Roosevelt.”

POTUSes were part of this thing? Say what?

So what was the Thirteen Club?

Source: Whatever Happened to The Thirteen Club?