The first catcher’s mask was worn in baseball in April 1877. Before that time, catchers sometimes wore tightly wound rubber bands around their teeth to protect them from getting knocked out.
As early as the 1860s pitchers began throwing faster and more deceptive pitches, like the curveball. In order to field them, catchers began moving closer to home plate. The rising velocity of pitches, in conjunction with catchers inching closer to the plate, significantly increased the risk for injury.
After watching his star catcher James Tyng get hit in the face one too many times, Harvard player/manager Fred Thayer modified a fencing mask which enabled the catcher to move closer to home without the fear of being struck in the face.