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Baseball diamond marines

A baseball diamond, seen from the stands

A baseball field or baseball diamond is the field upon which the game of baseball is played.


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. Traditionally, three canvas bags fifteen inches (38 cm) square marked the three bases. Major League Baseball began using 18-inch square (42 cm) bags in 2023, while most other forms of baseball continue to use the 15-inch bases. These three bags along with home plate form the four bases at the corners of the infield.

Baseball field overview thumbnail

Diagram of a baseball field.

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 closer to 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.

First Base[]

First base is the base to which the batter proceeds after hitting the ball. The base is usually guarded by the first baseman, who traditionally is a larger player with long legs and large hands. Since first basemen receive throws often but seldom need to make throws, it is often a position played by players who do not throw well.

A second line, called the "three-foot line", is drawn parallel to the foul line, starting from halfway between home plate and first base, and continuing to first base. The line is drawn on the foul side, three feet away from the foul line, as the name suggests. When the batter is advancing to first base after hitting the ball, and the defense is attempting to put the batter out at first base, the batter must run between the foul line and the three-foot line. If he does not do so, and interferes with the defense in any way, the interference is presumed to be intentional and the batter is out.

A special rule exists for batters running to first base: the batter, upon reaching the base, may overrun the base (continuing down the foul line) without liability to be put out, provided that they return directly to the base. This improves the odds for the batter to reach first safely, because they can run at full speed and not worry about stopping on the base. However, if the batter makes any move towards second base, he forfeits this immunity.

Second Base[]

Main article: Second baseman

Second base, or 2B, is the second of four stations on a baseball diamond which must be touched in succession by a base runner in order to score a run for that player's team. Second base is variously guarded by the second baseman and/or the shortstop, with the second baseman playing to the right of the base (as seen by the batter), and the shortstop to the left. The second baseman often possesses quick hands and feet, needs the ability to get rid of the ball quickly, and must be able to make the pivot on a double play. The shortstop, who on average will field more batted balls than any other position, also requires quick feet and hands, as well as a good throwing arm, (Shortstop is generally considered the most difficult fielding position, other than catcher.) Second base is also known as the keystone sack. In the numbering system used to record defensive plays, the second baseman is assigned the number 4.

Third Base[]

Main article: Third baseman

A third baseman, abbreviated 3B, is the player in the sport of baseball whose responsibility is to defend the area nearest to third base, the third of four bases a base runner must touch in a counterclockwise succession in order to score a run. In the numbering system used to record defensive plays, the third baseman is assigned the number 5.

Third base is often labeled as the "hot corner" due to the number of hard hit balls that right handed batters pull down the line.

Foul Poles[]


Third base foul pole.

The purpose of the foul poles is to help the umpire judge whether a fly ball hit above the fence line is foul (out of play) or fair (a home run). The poles are a vertical extension of the foul lines. Both objects are used to determine whether a ball is foul or fair, but the names are misleading, because both the lines and the poles are actually within 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 (shown 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 a foul line (most notably in left field) which might even sail higher than the foul pole. Sometimes, even repeated TV replays cannot prove the call either way.

Home plate[]

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. The left and right foul lines are aligned to the 45-degree edges of the plate, and come to a point directly behind the point of the plate. Contrary to what some fans think, all of home plate is in fair territory.

Three boxes are drawn in chalk near home plate. The lefthander's and righthander's batters boxes are 5 feet from front to back and 4 feet from left to right. The closest edge is 6 inches from the adjacent edge of home plate. The centers of the two boxes are horizontally in line with the center of the plate. At the start of a time at bat, the batter "stands in" the box of his choice (could be either box for a switch hitter). Once in place, the batter must remain there until his time at bat ends, unless he calls time (which he is allowed to do once per time at bat), has to dodge a pitch to prevent from being hit, or is removed for a pinch hitter. If a batted ball jumps up and hits the batter or his bat while he is still in the batter's box, it is a foul ball and the batter is not out. Conversely, if either foot is completely out of the box when the batter makes contact with the ball, he is out for improper batting.

The catchers's box is behind the plate. Its front edge is centered on the point of home plate; from here, it extends 8 feet back, and is 43 inches wide. Formerly, a rule required that when the defense chose to give the batter an intentional walk, the catcher had to remain within the box until after the pitcher released the pitch; if he left too early, this was called a catcher's balk, and it entitled the baserunners to advance one base. However, a 2021 rules change eliminated the need to actually throw pitches to intentionally walk the batter. Therefore the catcher's box no longer has any relevance to the rules, and some groundskeepers do not bother to chalk it.

Pitcher's Mound[]

Baseball pitch release

The pitcher moves forward off the rubber as the pitch is released.

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 rear 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 (as noted below). 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 the rear point of 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 rear point of home plate. Six inches (15.2 cm) in front of the pitcher's rubber the mound begins to slope downward. The top of the rubber is to be no higher than ten inches (25.4 cm) above home plate. From 1903 through 1968 this height limit was set at 15 inches, but was often slightly higher, sometimes as high as 20 inches (50.8 cm), especially for teams that emphasized pitching, such as the Los Angeles Dodgers, who were reputed to have the highest mound in the majors.

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. The lowering of the mound in 1969 was intended to "increase the batting" once again, as pitching had become increasingly dominant, reaching its peak the prior year; 1968 is known among baseball historians as "The Year of the Pitcher". This restrictive rule apparently did its job, contributing to the hitting surge of modern baseball.

In Little League Baseball, the distance between the mound and homeplate is 46'. On "Pony" fields, homeplate is usually located about 54' away. This adjustment each graduation between leagues prepares the youngster for the maximum distance of 60 feet 6 inches in high school baseball.

A pitcher's mound is difficult for groundskeepers to maintain. On youth and amateur baseball fields, the mound may be much different from 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, though it is not drawn in chalk or paint on the field (though foul lines are drawn). 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.

Grass line[]

Metrodome ALDS Oct 2004

The H.H.H. Metrodome, showing a white "grass" line.

The grass line marks the boundary between the infield and the outfield. On the infield side of this line, the surface is dirt; on the outfield side it is grass (or turf). The line is formed from drawing an arc of 95 feet in radius from the center of the pitching rubber.

With the advent of the Major League 2023 anti-shift rules, the grass line has gained a new significance in the rule book. The rules allow a maximum of three outfielders, which by definition are fielders who take up a defensive position on the outfield grass. Prior to this, the grass line was simply a visual and surface boundary between the infield and the outfield.

At one time, In artificial turf stadiums (such as those with FieldTurf in Major League Baseball), infield dirt along the basepaths was placed only in "sliding pits" around the bases, and the "grass line" was designated with a white line. Under current Major League and minor league rules, this type of field layout is no longer permitted.

Invisible infield center dividing line[]

This is an imaginary line, not actually drawn on the field, which extends from the point of home plate through the center of second base. Another aspect of the anti-shift rules, it divides the infield into left and right halves. When the pitcher delivers a pitch, there must be at least two infielders (excluding the pitcher and catcher) on each side of the line. A violation results in the pitch being called a ball, although if a play results, the offense can elect to take the result of the play.


The basic layout of the diamond has been little changed since the original Knickerbocker Rules of the 1840s. The distance between bases was already established as 90 feet, which it remains to this day. Through trial and error, 90 feet had been settled upon as the optimal distance. 100 feet would have given too much advantage to the defense, and 80 feet too much to the offense. As athleticism has improved on both sides of the equation, 90 feet remains the appropriate balance between hitting and fielding, as it continues to provide frequent tests between the speed of a batter-runner and the throwing arm of a fielder.

It is the pitching distance, and other aspects of the pitcher's mound, and of pitching itself, that have been tinkered with from time to time over the many decades, in an effort to keep an appropriate balance between pitching and hitting.

In contrast to the distance between the bases, which seems natural enough, the very specific pitching distance of 60 feet 6 inches is one of those sports oddities that seems like a mistake unless one knows the history:

  • 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; he could not run in from the field as bowlers do. Furthermore, he had to throw underhand. By the 1880s, pitchers had mastered the underhand delivery quite well. The year 1880 saw two perfect games within a week of each other.
  • 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. Pitchers were allowed to throw overhand starting in 1884, and that tilted the balance of power again. 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, thus somewhat restricting his ability to "power" the ball with his overhand delivery.
  • In 1893, the box was replaced by the pitcher's plate, although the term "knocked out of the box" is still sometimes 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 hopefully to increase attendance, as fan interest had flagged somewhat), resulting in the peculiar pitching distance of 60 1/2 feet.
  • Many sources tend to say that the pitching distance evolved from 45 to 50 to 60 1/2 feet. However, the first two were the "release point" and the third is the "pushoff point", so the 1893 increase was not quite as dramatic as is often implied; that is, the 1893 rule change added only 5 feet to the release point, not 10 1/2 feet.
  • 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.

See also[]


  • Official Rules of Major League Baseball
  • The Baseball Encyclopedia, published by MacMillan
  • Glory Fades Away, by Jerry Lansch

External links[]