Copy Link As the 2021 season approaches, MiLB.com introduces the 11 leagues created by the restructuring of Minor League Baseball across four levels of play. Below is a team-by-team introduction to the High-A East, including affiliation, previous circuit and most recent championship. (Note: Established refers to the first year of a team s As the 2021 season approaches, MiLB.com introduces the 11 leagues created by therestructuring of Minor League Baseball across four levels of play. Below is a team-by-team introduction to the High-A East, including affiliation, previous circuit and most recent championship. (Note: Established refers to the first year of a team s continuous operation in that market regardless of league or level.) Learn about other leagues here:Triple-A East, Triple-A West, Double-A Northeast, Double-A Central, Double-A South.