Why is it called home plate?

Every journey needs a starting place. Where better to start than home? If you think about it, the game does seem to revolve around home plate. Balls and strikes are called based on its size, pitches are thrown over it, and batters touch it last to score a run. You can’t “touch ‘em all” without home plate, a called strike three doesn’t exist without something to determine what it’s called, and a grand slam doesn’t mean anything until all four runners step on home. So what’s with the name, why isn’t it home base? And let’s be honest, it doesn’t look anything like a plate.

First things first: why not home base? Well, that’s because it originally wasn’t a “base,” it was a plate. Literally. Home was an iron plate in the ground, thus the name. In fact, the rules in the 1857 called for a round plate of iron, as the New York Herald reported in 1859: “The home base is marked by a flat circular iron plate, painted white.” So the only think connecting the appearance of home plate then and now was the fact that it was white.

In 1858, home plate became a 12”x12” square iron plate, still painted white. A few years later in 1872, the plate was rotated so the point faced the pitcher. The material became a problem when sliding became common in the 1880’s. Sliding into a soft bag wasn’t a big deal, but sliding on top of a raised piece of iron with sharp corners all of the sudden doesn’t sound like such a great idea. In 1885 the American Association prescribed a rubber “plate” instead of the old iron plate. A few years later when the various leagues consolidated their rule books, they decided to agree on a white, rubber 12”x12” square for home plate. It wasn’t a plate anymore, but the name stuck.

The last change was the shape, from a square to the familiar 5-sided pentagon of today. Before the 1900 season, the new shape was introduced with the flat part facing the pitcher. Spalding’s Official Base Ball Guide from 1900 stated the reason was that it “enables the pitcher to see the width of base he has to throw the ball over better than before, and the umpire can judge called balls and strikes with less difficulty.” The new shape didn’t change the width of the strike zone at all, just made it easier for pitchers to see what they were aiming at and easier for umpires to make the calls (insert own joke about the eyesight of umpires here…). Credit for the new design is hard to place, but the best bet might be umpire Michael McMahon, who seemed to be given credit at the time. The only difference was that he felt the flat part should face the catcher, not the pitcher. So if it was in fact his idea, he’ll get the credit for the shape we see today, just not the orientation.

The shape was so good that the only change to home plate since the 1900 season was in 1936, when the rules specified the addition of beveled edges of the plate. The 2009 Official Rules of Major League Baseball give the exact specifics of home plate, relatively unchanged from the 1900 season:

"Home base shall be marked by a five-sided slab of whitened rubber. It shall be a 17 inch square with two of the corners removed so that one edge is 17 inches long, two adjacent sides are 8 1/2 inches and the remaining two sides are 12 inches and set at an angle to make a point. It shall be set in the ground with the point at the intersection of the lines extending from home base to first base and to third base; with the 17-inch edge facing the pitcher’s plate, and the two 12-inch edges coinciding with the first and third base lines. The top edges of home base shall be beveled and the base shall be fixed in the ground level with the ground surface.” (Rule 1.05)

Included is Diagram 2 from the 2009 Official Rules of Major League Baseball for reference:

Notes: When measuring the distance to the pitcher’s mound (60 ft, 6 in), 1st/3rd base (90 feet), or straight across to 2nd base (127 ft, 3 3/8 in), the back point of home plate is where the measurement starts.

Since all of home plate is in fair territory, a ball hit off of home is considered in fair territory.

Sources:

Morris, Game of Inches (Vol. 2)
http://www.baseball-almanac.com/stadium/baseball_field_construction.shtml
2009 Official Rules of Major League Baseball