College basketball takes center stage on the sports calendar each March as the NCAA basketball tournament gets underway. The tournament brings a packed three weeks of high-pressure games as 68 teams compete for the college basketball crown. Along the way, millions of Americans fill out brackets, join office pools, and tune in to games as March Madness unfolds.

For most of the rest of the year, professional sports are more popular among U.S. sports fans. According to polling from Gallup, professional football is America’s most popular sport, with 62% of Americans identifying as fans, and professional baseball is close behind with 57%. And the two less popular major pro sports, basketball and hockey, have each trended upward significantly in popularity over the last two decades. Meanwhile, both college football and college basketball lag slightly behind their professional equivalents in popularity.

One caveat to this data is that sports fandom in the United States can be highly regionalized, with varying interest in different professional sports or in college athletics depending on location. The four major sports leagues—Major League Baseball, National Basketball Association, National Hockey League, and National Football League—together contain 124 franchises across the United States and Canada. But these professional franchises are concentrated in a relatively limited number of locations. Most of the markets where professional franchises set up shop have large populations, strong TV markets, and residents with disposable income to support ticket and merchandise sales. And many markets have been found to be well-suited for some sports but not others—like football in Jacksonville or basketball in Portland.

As a result, nearly half of all professional sports franchises are based in just seven U.S. states—and in particular, the seven with the most residents. California and New York not only have multiple metro areas that are able to support professional sports franchises but, in the cases of Los Angeles, the Bay Area, and New York City, also have metro regions large enough to sustain multiple franchises in the same sport. Among smaller states with professional sports, it is more common to have a lower number of sports or teams represented. Four states have only two professional teams and another four have only one.