American Association of Independent Professional Baseball
The American Association was founded in 2005 and played their first games in 2006. The league has teams in Texas, Kansas, Louisiana, Indiana, Iowa, Nebraska, North Dakota, South Dakota, Minnesota and Manitoba. The North, Central and South Divisions are home to 14 teams.
The league recently saw their 150th player reach the major leagues which is quite an accomplishment since only beginning games in 2006.
One very interesting thing about this league is the restrictions they have on individual team rosters. Players are given a status based on their service time and teams can only have a limited number of 'veteran' players. These restrictions play a similar role to the salary caps found in Major League Baseball as an attempt to maintain parity throughout the league.
The Frontier League began in 1993 and currently has 12 teams. Frontier League teams have a salary cap of $72,000 (for a 24 man roster) and the league minimum for pay is $600 per month. It is due to this low pay that players typically live with 'host families'. These families are often big fans of the team and offer players a free place to stay.
Frontier League teams can be found in Michigan, Illinois, Ohio, Pennsylvania, Indiana, Kentucky and Missouri. Stadium capacity for the team’s baseball parks range from 3,200 to 7,000.
The Atlantic League was founded in 1998 and currently has only 8 teams. There are plans to expand to 10 teams with new parks opening in Texas and Virginia. Right now there are teams primarily in the Northeast: New Jersey, Pennsylvania, Connecticut, New York and Maryland. In spite of the low amount of teams many consider the Atlantic League to field teams that possess a higher level of play than their independent counterparts. The salary caps for players are also higher and team facilities are often more accommodating. Some Atlantic League players who made it to the Majors include: Ruben Sierra, Carlos Baerga, Junior Spivey, Randall Simon, Mark Whiten, Shea Hillenbrand, Keith Foulke among others.
The Can-Am or Canadian American League is home to 8 different teams. The Can-Am League has similar 'Length of Service' restrictions as other independent leagues, preventing any one team from possessing most of the veteran talent. There is also a general player salary cap that prevents teams from simply out-spending each other. This salary cap leads teams to allow players to act as coaches for a little extra pay, instead of teams hiring multiple coaches. The teams can be found primarily in the Northeast: Massachusetts, New Jersey, Quebec and New York.
North American League
The North American League will begin play this season after being founded in 2010. Three leagues combined to form the NAL: the Golden Baseball League, the Northern League of Illinois and the United baseball League of Texas. By combining the leagues and adding a new team the league is able to field 2 divisions (North & South) of 5 teams each. One interesting note about the NAL is that they have a team in Hawaii. The Na Koa Ikaika Maui will play in a stadium with a 1500 capacity.
The Pecos League is the most isolated Independent League in the US with all but one of their teams residing in New Mexico. Of the six teams in the league the lone outsider plays in nearby Texas. The league boasts high scoring games as a result of playing in such high altitude regions. I believe the Pecos League is the only Independent League to offer fantasy baseball for their fans.