On June 27, 1911, there was an unintended consequence of an attempt to speed up the game. American League president Ban Johnson had issued a directive that warm-up pitches were now banned, because they were time-wasters. Once the batter stepped into the box, any pitch that was thrown would count.
On June 27, Stuffy McInnis moved into the batter's box and smacked a warm-up pitch before any of the fielders were in position. He ran around the bases for an inside-the-park home run. It was after this incident that Ban Johnson vacated the edict, and warm-up pitches were again allowed.
The 20-second rule has been in the books since 1901. Attempts to speed up the ballgame date back to the 1850s, with the introduction of called strikes, so that batters wouldn't let good ones go by, and waste time. In 1864, there was the introduction of called balls, because pitchers were wasting time by nibbling outside of the plate, trying to get batters to swing at an unhittable pitch.
The current obsession with the time and the pace of the game, like with most things in baseball, isn't new.
May 30, 2016
Attempts To Speed Up Baseball Games Date Back 160 Years
From John Thorn, MLB's Official Historian: