Single-A

Single-A, formerly known as Class A and sometimes as Low-A, is the fourth-highest level of play in Minor League Baseball in the United States, below Triple-A, Double-A, and High-A.

[1] Class A was originally the highest level of Minor League Baseball, beginning with the earliest classifications, established circa 1890.

[2]: 15  When the National Association of Professional Baseball Leagues – the formal name of Minor League Baseball – was founded in 1901, Class A remained the highest level, restricted to leagues with cities that had an aggregate population of over a million people.

In 1965, a Class A Short Season designation was created, for teams playing June–September schedules, primarily meant for new players acquired via the amateur draft.

Following MLB's acquisition of the rights to the names of the historical minor leagues, MLB announced on March 16, 2022, that the leagues would revert to their prior names, effective with the 2022 season.