This is the field upon which the game of Baseball is played.

The pitching distance of 60 feet 6 inches is one of those sports oddities that seems like a mistake unless one knows the history. To paraphrase Mae West, "Never mind the 60 feet, let's talk about the 6 inches":

• The original Knickerbocker Rules did not specify the pitching distance explicitly.
• By the time major league baseball began in the 1870s, the pitcher was compelled to pitch from within a "box" whose front edge was 45 feet from the "point" of home plate. Although he had to release the ball before crossing the line, as with bowlers in cricket, he also had to start his delivery from within the box, not run in from the field as bowlers do.
• In an attempt to "increase the batting", the front edge of the pitcher's box was moved back 5 feet in 1881, to 50 feet from home plate.
• The size of the box was tinkered with over the next few years. In 1887, the box was set at 4 feet wide and 5 1/2 feet deep, with the front edge still 50 feet from the plate. However, the pitcher was compelled to deliver the ball with his back foot at the 55 1/2 foot line of the box.
• In 1893, the box was replaced by the pitcher's plate, although the term "knocked out of the box" is still used when a pitcher is replaced for ineffectiveness. Exactly 5 feet was added to the point the pitcher had to toe, again "to increase the batting", and thus resulting in the peculiar pitching distance of 60 1/2 feet in baseball.
• Originally the pitcher threw from flat ground (as softball pitchers still do), but over time the mound was developed, tipping the balance back the pitchers' way somewhat.

(Sources: Glory Fades Away, by Jerry Lansch; The Baseball Encyclopedia, published by MacMillan).

The starting point for much of the action on the field is home plate, which is a five-sided white rubber slab 17 inches by 8 1/2 by 12 by 12 by 8 1/2 inches. Next to each of the two parallel 8 1/2 inch sides is a batter's box. The point of home plate where the two 12 inch sides meet at right angles, is at one corner of a ninety-foot square. The other three corners of the square, in counterclockwise order from home plate, are called first base, second base, and third base. Three canvas bags fifteen inches (38 cm) square mark the three bases. These three bags along with home plate form the four bases at the corners of the infield.

A subtlety about the bases is that home plate and the first and third base bags are entirely within the ninety-foot square. They are positioned this way to help the umpires, as any ball hitting those bases must necessarily be in fair territory. Home plate has its peculiar shape in order to help the plate umpire judge whether a pitch is over the plate or not, i.e. whether it might be in the strike zone. The second base bag, which is fully within fair territory, is placed so that its center coincides exactly with the corner or "point" of the ninety-foot infield square. Thus, although the "points" of the bases are 90 feet apart, the physical distance between each successive pair of base markers is more like 88 feet.

The lines from home plate to first and third bases are extended to the nearest fence, stand or other obstruction and are called the foul lines. The portion of the playing field between (and including) the foul lines is fair territory; the rest is foul territory. The area in the vicinity of the square formed by the bases is called the infield; fair territory outside the infield is the outfield. Most baseball fields are enclosed with a fence that marks the outer edge of the outfield. The fence is usually set at a distance ranging from 300 to 410 feet (90 to 125 m) from home plate. Most professional and college baseball fields have a right and left foul pole. These poles are at the intersection of the foul lines and the respective ends of the outfield fence.

The purpose of the foul poles is to help the umpires judge whether a fly ball hit above the fence line is fair (a home run) or foul (out of play). The foul pole is an extension of the foul line. Despite their names, both the foul lines and the foul poles are actually in fair territory. Prior to 1920, the foul lines were "infinite": A fly ball over the fence had to land in fair territory, or to be fair when last seen by the umpire, in order to be a home run. The rule was changed to be where the ball is when it clears the fence. Thus, a fly ball hitting a foul pole above the top of the outfield fence is a home run, regardless of where the ball goes after striking this pole, and a fly ball clearing the fence on the fair side of the pole is a home run regardless of where it lands. Foul poles (not shown on the diagram seen above) are typically much higher than the top of the outfield fence, and often have a narrow screen running along the fair side of the pole to further aid the umpire's judgment. It can still be a difficult call, especially in ballparks with no outfield stands behind the poles to provide perspective. Wrigley Field is notorious for arguments over long, curving flies down the lines which might even go higher than the foul pole. Sometimes, even repeated TV replays cannot prove the call either way.

For the Bonnie Raitt album, see Home Plate. For the geological feature on Mars, see Home Plate (Mars).

In baseball and related games, home plate is the final base that a player must touch to score. It has five sides. Unlike the other bases, home plate is hard, usually a slightly flexible hard plastic with beveled edges that rises only slightly above ground level.

In the middle of the square is a low artificial hill called the pitcher's mound. On the mound there is a white rubber slab, called the pitcher's plate or commonly the rubber, six inches (15 cm) front-to-back and two feet (61 cm) across, the front of which is exactly sixty feet six inches (18.4 m) from the point of home plate. This peculiar distance was set by the rulemakers in 1893, not due to a clerical or surveying error as popular myth has it, but purposely (see Pitcher's mound for a detailed history of the pitching distance). On a baseball field, the pitcher's mound is a raised section in the middle of the diamond where the pitcher stands when throwing the pitch.

In Major League Baseball, a regulation mound is 18 feet (5.5 m) in diameter, with the center 59 feet (18.0 m) from home plate, on the line between home plate and second base. The front edge of the pitcher's plate or rubber is 18 inches (45.7 cm) behind the center of the mound, making it 60 feet 6 inches (18.4 m) from the plate. Six inches (15.2 cm) in front of the rubber the mound begins to slope downard. The rubber is also never more than ten inches (25.4 cm) high, although previously to 1969 it was often at 16 inches (40.6 cm) or even 20 inches (50.8 cm).

A pitcher will push off the rubber with his foot in order to gain velocity toward home plate when pitching. In addition, a higher mound generally favors the pitcher over a lower mound. With the height advantage, the pitcher gains more leverage and can put more downward velocity on the ball, making it more difficult for the batter to strike the ball squarely with the bat. Thus, the lowering of the mound in 1969 is thought to be a contributing factor to the hitting surge seen in modern baseball.

A pitcher's mound is difficult for groundskeepers to maintain. On youth and amateur baseball fields, the mound may be much different than the rulebook definition due to erosion and repair attempts. Even in the major leagues, each mound gains its own character, as pitchers are allowed to kick away pieces of dirt in their way, thereby sculpting the mound a bit to their preference.

A baseline is the direct route—a straight line— between two adjacent bases. The basepath is the region within three feet (0.9 meters) of the baseline. Baserunners are not required to run in this objective basepath, however; a baserunner may run wherever he wants when no play is being attempted on him. At the moment the defense begins to attempt a tag on him, his running baseline is established as a direct line from his current position to the base which he is trying for. The runner may not stray three feet away from this line in an attempt to avoid a tag; if he does, he is automatically out.

The grass line, where the dirt of the infield ends and the grass of the outfield begins, has no special significance to the rules of the game. Its only purpose is to act as a visual aid so that participants, fans, and umpires may better judge distance from the center of the diamond.

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