Understanding the arrangement of American sports leagues is key to knowing what’s happening. Most of the sports are played in seasons, which are arranged into two leagues that clash at the final championship game.

Today we’re looking at how that works in Major League Baseball and the roles that the National League and the American League play, along with their history. Knowing the structure of baseball is also important for those who are placing bets. If that’s you, check out Fanduel’s MLB sportsbook.

The Major League

The way baseball was played was standardized after the American Civil War, where soldiers had played the game in camps all over the nation. From this came the sport’s first governing body, the National Association of Base Ball Players, or NABBP. It was an amateur league based mainly in the Northeastern United States that spanned 400 clubs.

As for pro baseball, the official start is 1869. This is when the first-ever pro baseball team was started, the Cincinnati Red Stockings. From there, the NABBP went professional as the National Association, or NA, while the National League of Professional Base Ball Clubs was founded and became known as the National League, or NL for short. The NL outcompeted the NA. 

As the NL found success over the 1880s and 90s, their biggest competitor was the American Association, or AA, who offered alcohol to spectators. Both the NL and the AA went at each other in a postseason championship series. The AA was absorbed into the NL in 1892.

After several teams dropped away from the NL, the American League was then founded in 1901 and a bidding war broke out. By acquiring more teams across America’s cities, the many fledgling baseball leagues were attempting to distinguish themselves as major leagues and not minor leagues.

The American League was one of the most successful competitors to the National League. Tensions subsided when both leagues agreed to host the first-ever World Series in 1903 and recognize each other as the two Major Leagues, with any alternative organizations being characterized as minor leagues.

Since then, the two leagues have functioned just like conferences do within American football, as two distinct outfits that compete amongst themselves and then clash at the end of the season. They are the two halves of the whole that we now call Major League Baseball.

The National League

So, now that we have a broad understanding of the Major League, let’s go into more detail about its two sections. First, the National League, which is the world’s oldest sports league that’s still going today after its founding in 1876. As we mentioned above, the full name is the National League of Professional Baseball Clubs. It’s also called the Senior Circuit by many.

The National League was formalized by Chicago businessman and White Stockings officer William A. Hulbert, who took the flagging league and took them to four and then eight charter members.

After the Major Leagues were established, the National League grew from 8 to 15 teams across the United States. They are separated into East, Central, and West subdivisions to make management and competition between them easier.

Here are the teams currently in the National League.


  • Atlanta Brewers
  • Miami Marlins
  • New York Mets
  • Philadelphia Phillies
  • Washington Nationals
  • Chicago Cubs
  • Cincinnati Reds
  • Milwaukee Brewers
  • Pittsburgh Pirates
  • St. Louis Cardinals
  • Arizona Diamondbacks
  • Colorado Rockies
  • Los Angeles Dodgers
  • San Diego Padres
  • San Francisco Giants.


The American League

As for the younger of the two Major Leagues, the American League of Professional Baseball Clubs is referred to as the American League or the Junior Circuit, because it’s 25 years younger than the National League.

The American League started as a success story, a minor league that was transformed by Ban Johnson into a major league by competing with the pre-established NL. Having also started with 8 teams, they also have 15 teams split over East, Central, and West groupings. Here are the current AL teams. You’ll notice that some, like the Yankees and the Mets, are even based out of the same city!


  • Baltimore Orioles
  • Boston Red Sox
  • New York Yankees
  • Tampa Bay Rays
  • Toronto Blue Jays
  • Chicago White Sox
  • Cleveland Indians
  • Detroit Tigers
  • Kansas City Royals
  • Minnesota Twins
  • Houston Astros
  • Los Angeles Angels
  • Oakland Athletics
  • Seattle Mariners
  • Texas Rangers