Baseball is a sport rooted in rules and regulations. Everything in the game is standardized, planned, and coordinated, based on a guideline or precedent. Everything, that is, but the park itself: outfield sizes and wall heights vary across the entire league. There are 30 MLB stadiums. No two of them are alike.

In most professional sports, the playing surface and goal size are the same everywhere the game is played. Hockey nets are 178 feet apart. Basketball hoops are ten feet above the hardwood. And American football fields are 100 yards long. Not when it comes to baseball fields, though.

Once you leave the infield, where the pitcher's mound is always 10 inches high, and the bases are always 90 feet from each other, the major leagues have few discernible rules regarding field size or fence height. Pro ballparks come in all shapes and sizes, sometimes due to the shape of the city block on which they were built, sometimes just to add character.

Just check out how much variation exists in the fence heights of all 30 stadiums across left, center, and right field.

Each fence has a story to tell. In older stadiums, higher fences were often built in shorter sections of the outfield to prevent easy home runs, and in some cases, owners adjusted outfield walls between seasons based on their team's strengths. In modern retro parks, artificial quirks are added to the outfield fence and boundary, sometimes to make room for features like swimming pools or Coors Field's Rockpile, and sometimes purely for aesthetics.

The inconsistencies and idiosyncrasies of pro baseball fields have fascinated me for years. In this piece, the first in a series on the irregular outfields of baseball, I look at the seven different types of MLB parks, what makes them distinct, and where the varying sizes in their outfields come from.