Major League Baseball, like many other major sports groups, is a franchisor. What this means is that expansion teams are only added when they pay to be part of the pool, bringing a new city into the mix as a potential champion.

When the league was formed, there were only 16 teams, all of which were in the East and St. Louis. But between the start of the leagues and today, the population of the West has more than doubled. Those residents of Oakland, San Francisco, Denver, Phoenix, LA and other Western cities also wanted representation. Some teams from the east moved west (SF Giants), but most didn’t want to. What were cities to do? They got expansion teams.

Expansion teams generally perform terribly during their first few seasons. New teams don’t have the money to bring big names to their cities, and because they’re new, they have the last pick in the draft. What that means is that the handful of new expansion teams compete with each other to get the best of a lackluster lineup of talent. However, it’s not impossible to succeed in a few short years: The Arizona Diamondbacks were founded in 1998 and won the World Series in 2001. That said, this is the exception to the rule.

The first two expansion teams were brought in in 1961, and MLB has seen additions every few years since then. The most recent additions were in 1998. The current team roster has grown from its original 16 to 30.

1961: LA Angels of Anaheim (brought over as Anaheim Angels) and Texas Rangers (originally Washington Senators)

1962: Houston Astros (formerly the Houston Colt. 45’s) and New York Mets

1969: Washington Nationals (signed as Montreal Expos), San Diego Padres, Kansas City Royals, and Milwaukee Brewers (who started as Seattle Pilots)

1977: The Seattle Mariners and the Toronto Blue Jays

1993: Colorado Rockies and Florida Marlins

1998: Arizona Diamondbacks and Tampa Bay Rays (formerly Tampa Bay Devil Rays)