High Quality Content by WIKIPEDIA articles! The Atlantic League of Professional Baseball is a professional, independent baseball organization located primarily in the Mid-Atlantic and Northeastern United States, especially the greater metropolitan areas of the Northeast megalopolis. It operates in cities not served by Major or Minor League Baseball teams and is not affiliated with either. The Atlantic League requires cities to have the market for a 4,000 to 7,500-seat ballpark and for the facility to be maintained at or to exceed AAA standards. The level of Atlantic League play can be categorized as between AA and AAA.