(Via the New York Times)

Earlier this month, Facebook put out a map denoting the geographic outlines of every MLB team’s fan base, as determined by the team with the most Facebook likes per county. The map revealed that the geographic area of the Nationals’ fan base is one of the smallest in baseball.

The New York Times has improved upon the Facebook map by crunching the data at the Zip code level. Hovering over the Times’ extremely cool interactive map reveals the top three teams, as a percentage of total Facebook likes, for each Zip code.

In 20003, home of Nationals Park, the top three teams are the Nationals (36 percent), Yankees (14 percent) and Red Sox (10 percent). In 21201, home of Camden Yards, the top three teams are the Orioles (67 percent), Yankees (11 percent) and Red Sox (4 percent).

The Times dubs the bold white line in the graphic above — the border between Nationals and Orioles country, by this measure — the Line of Potomac Aggression.

Via the New York Times

After the departure of the Senators in 1971, Washingtonians spent decades alternately lamenting their plight and treating the Orioles as their home team. That era is over. While the Orioles have held onto many Maryland suburbs, the Nats now dominate Washington and much of the Virginia suburbs. In parts of the Washington region, the Orioles aren’t even the second-favorite team; the Yankees or the Red Sox are.

Explore the interactive map here.