This visualization by Tom Giratikanon, Josh Katz, David Leonhardt, and Kevin Quealy shows us how far the actual territory of each MLB team reaches. The New York Times created this map with ZIP codes of people who ‘liked’ each team’s Facebook pages.
It might not be a perfectly accurate visualization of actual fandom since the data was scraped from social media, which means it might be biased to include more of the younger generation of baseball fans. However, it still gives a rough look of how fans are distributed all over the country. Borders in this map don't exactly fit state border lines, and it is interesting to guess why a specific team has more fans in particular areas(for example, the range of television broadcast for a team plays a huge role in the distribution of its fandom). Also, this map shows the universal love of Americans for the New York Yankees.
At first, you will see a general distribution of fandom by color over the map, and you can discover deeper levels of information as you play with it. If you zoom in a bit, you can hover your mouse over the map to see percentages of top 3 teams in the particular county.
If you zoom in more, finally you’ll be able to check percentages of top 3 teams for individual ZIP codes. Find your town and see how many of your neighbors are rooting for the same team that you like!
Also, it is particularly interesting to see borders between neighboring rivals. Yankees vs. Red Sox & Mets(sadly there is not a single area for Mets), Cubs vs. White Sox for example.
If you are interested, you can also read the analysis of the map detailing some additional findings.