When the spitball was outlawed, some pitchers were granted permission to throw spitballs for the rest of their careers. Who was the last one?

The spitball was once legal and used commonly. The pitch was banned before the 1920 season, but 17 pitchers who used it regularly were allowed to continue to do so until they retired. The last pitcher to employ the pitch was Burleigh Grimes, who retired in 1934 after 19 seasons.