New baseballs are far too slick for pitchers to grip properly, and during the early days of the sport, various solutions to this problem were trialed, including glossing them with tobacco juice or shoe polish for added grip.
Nothing seemed to do the trick until a little-known player turned-coach named Lena Blackburne stumbled upon a strange mud while walking near a tributary of the Delaware River. He scooped some up, took it home, applied it to one of his baseballs and found it was just the thing to make slippery pitching a thing of the past.
By 1938, every team in the American League had adopted Blackburn Rubbing Mud, but the man himself never revealed the location of his source to anyone within the sport. Only his business partner John Haas was let in on the secret.
These days, Major League Baseball relies on the rubbing mud, but only two people know where it originates from: the company's current owner Jim Bintliff - who visits the source once a year and returns with 1,000 pounds of the substance - and his wife.