What Are Ground Rules in Baseball?

Beyond the Bases: Uncovering the Intriguing World of Baseball's Ground Rules
Written by Mark Bailey
Last updated on

Ground rules in baseball are unique guidelines established for each ballpark that dictate how play proceeds when a ball is affected by specific elements or areas within the field. From quirky outfield angles to bullpen interference, these rules ensure fair play in each distinctive venue. Let’s explore the quirky, essential, and sometimes game-altering ground rules across the majors.

  • Ground Rules are specific rules for each individual stadium and can include field dimensions, dugouts, safety netting, outfield walls, live trees, and more.
  • They are created through a collaboration of team ownership, stadium architects, and the local environment.
  • Umpires, teams, and fans must follow any special ground rules that MLB approves for each stadium.
  • Other unique ground rules include on-the-spot manager creations (e.g., allowing fans on the field) and recognizing retractable roofs with regard to opening/closing conditions.
  • These varied rules are put in place to clarify uncommon situations arising due to the unique features of stadiums.

Definition of ground rules

The official MLB definition of ground rules is: “The Commissioner’s Office issues a list of universal ground rules that are to be used in every Major League ballpark each season. Individual parks then are able to institute their own special ground rules, covering instances in which intricacies of said parks might influence the game.”

What this means is that for stadium similarities (dugouts, protective netting, etc.) that do not change from one stadium to the next, they follow the universal rules. However, the universal rules do not include the left field corner in San Diego described above or the stadium roof in Tampa. To keep it organized, each team submits its own ground rules to MLB, which then approves and lists them for umpires, teams, players, and fans to access. You can see it here.

How ground rules are established

Ground rules for each individual stadium are created through a collaboration of team ownership, stadium architects, and the local environment. It is argued that field dimensions are the most common and important of all ground rules. Do you know why the original Yankee Stadium was popularly referred to as “The House That Ruth Built”? The Bambino hit left-handed and crushed home runs to right field. So, the Yankees made sure when they built the stadium in 1923, the right field wall was the shortest part of the outfield with a short wall.

Changes in game technology have also had a huge impact on ground rules. Aside from TV cameras, stadiums have 12 cameras used to detect and trackball and player movement. Depending on where they are located, they may or may not be in play; it depends on the ground rules for that stadium. 

Types of ground rules

Aside from using the field dimensions and stadium quirks to determine what is a home run, what’s out of play, and what’s considered a ground rule double, there are other kinds of requirements.

1. Teams must include photos of their dugouts, safety netting, outfield walls, and other unique stadium features so that visiting teams and umpires can familiarize themselves. Each MLB team submits these photos to the league at the beginning of the season.

2. Some teams add live trees to their ground rules. Ponce De Leon Ballpark in Atlanta (demolished in 1966) was modern for its time, except for one thing. To date, this park is the only one in history that was allowed to have a large magnolia tree in the outfield and have it be in play. Fun fact: Who was the first player to hit the ball into the tree? Babe Ruth hit a tree on a fly ball during a preseason exhibition game. That is what baseball announcers refer to as a bomb.

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3. Some managers create ground rules right on the spot with the help of the umpire. Consider this example from the 1903 World Series when the Pittsburgh Pirates faced the Boston Americans: The Series was highly anticipated because of the matchup of Cy Young versus Honus Wagner. However, Exhibition Park in Pittsburgh couldn’t handle the massive crowds. So, the fans decided to watch the game standing on the field. The Pittsburgh police came, but the fans weren’t leaving, so manager Fred Clarke came up with rules on the spot that included players playing with fans on the field. It also marks the first-ever ground-rule-triple established in MLB.

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Importance of ground rules

Ground rules are important to players, umpires, and fans because in competitive sports, clarity matters. Ground rules are in place to take away ambiguity and provide answers for the little questions that come up in each ballpark: “What happens if the ball is hit here but bounces over there?”

By understanding these rules, teams can either exploit them on offense or try to play to their quirks defensively.

Challenges with ground rules

Outside of having to know the rules for each stadium (Umpires travel all season, they don’t have a home stadium), a bigger issue is the ground rules that involve judgment calls. These are commonly inconsistent. Baseball will always be strange, but consistency is a goal that can be achieved. In that spirit, let’s discuss Pittsburgh again.

PNC Park has a section of the left-centerfield wall that has a unique 90-degree angle built into the wall. Because of that, a batted ball that hits one side of this angled section and bounces over the wall is a home run… until it isn’t. If the ball hits one of the angled walls but is too low, even if it still bounces over the wall, it is only two bases. Here are last season’s official ground rules at PNC, approved by MLB:

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Why are they called ground rules?

The term “ground rules” came into popular use in the 1890s to designate rules that applied to a specific field. The first team to use the phrase was the Baltimore Orioles, who, according to historians, played on a field that was just dirt over concrete around home plate. Thus, the Baltimore Chop was born.

Why are ground rules important in baseball?

Ground rules are important in baseball because they clarify what is supposed to happen if an uncommon situation arises because of a unique feature of a field or stadium.

What is the most complicated ground rule in baseball?

The most complicated ground rule in baseball involves retractable roofs. Players, umpires, and fans can familiarize themselves with the dimensions of the field and what is considered a home run, a double, or a dead ball. However, none compare to the complexity of opening and closing the roof. 

For fans of the Mariners, Blue Jays, Brewers, D-Backs, Astros, Marlins, and Rangers, this excerpt is for you: “For ballparks with retractable roofs…The roof can be closed only for weather reasons if the game begins with the roof open. If the game begins with the roof closed, it can be reopened once the home team determines the climatic environment has reached a level where fan comfort and enjoyment will be best served by opening the roof. The roof may be moved only once during a game unless inclement weather indicates otherwise. During the postseason, the Commissioner or another designated official shall make all decisions regarding roof movement, in consultation with the home club and the umpire crew chief.”

Sorry Astros fans, this rule was created because of Minute Maid Park.


Unlike international baseball leagues where stadiums are symmetrical, MLB believes in creative freedom. The history of MLB contains many unique rules that applied anywhere a game was played (including some never intended for baseball). Some ground rules get made up on the spot, and some are created because players perform jumping jacks to distract hitters, while others try stealing bases in reverse (Yep – both are true). 

The great thing about baseball is that modern visionaries are still incorporating that historical weirdness into today’s game. That is, unless you build a huge hill in the middle of centerfield with a steel flagpole in fair territory. Fans in Houston loved Tal’s Hill and just about no one else.

Just when you thought MLB had all the quirks, if you ever find yourself in Buffalo, NY, and have free time, check out the field that Canisius College plays on. Yes, you are seeing two diamonds on a single L-shaped field. The designers of the Polo Grounds in NY would be proud.