1858
In the earliest days of baseball, there was no rubber at the pitcher's mound. Pitchers stood inside a six-foot square that looked much like today's batter's box. The front line of the box was only 45 feet from the plate. (The batters were also allowed to call their pitches -- high, low or fair.)
1881
Baseball moved the front of the pitcher's box back to 50 feet.
1887
Baseball made the box smaller and batters were no longer allowed to call for their pitches.
1893
Baseball replaced the pitcher's box with the pitcher's plate. The plate was set at 5 feet behind the back line of the pitcher's box. The theory of the distance is that the proposal was to move it 60 feet, but a groundskeeper misread the number and put it at 60 feet, 6 inches from the mound.
1903
The height of the pitching mound was set at no higher than 15 inches.
1968
After one of the most dominant years for pitchers in baseball (both league MVPs were pitchers), the mound was reduced to 10 inches tall.