Here's a map of minor league baseball attendance last season, made by Redditor rbhindepmo. The data comes from marketing analyst David Kronheim, who has put together baseball attendance reports since 2009.
The attendance figures come from MLB affiliated farm teams and from five independent leagues: the American Association, Atlantic League, Frontier League, Can-Am League, and the United League of Baseball. Attendance figures from other indie leagues were incomplete and not included, according to the Reddit post.
Ignore the syntax, which is a little confusing. The first number tells you the attendance per game. The second number tells you how many games were played in that state. The Northeast and much of the Midwest have the highest attendance figures. Southeast states tend to have lower attendance. California and Florida have a high number of games because of the California League and the Florida State League.
Mexico and Canada had minor league baseball last season, but a few states didn't. Wyoming is the only state among the 48 contiguous states to have no minor league baseball. Hawaii and Alaska also do not host any games, although Alaska still sees many of baseball's best prospects when college players play there in the summer.
[Reddit]