In the months leading up to the 1971-72 school year, seven schools collaborated on the possibility of forming a new athletic conference. Agreement was reached and the Southwestern Athletic Conference was born. Original members of the conference included Bloomingdale, Decatur, Gobles, Lawton, Lawrence, Marcellus and Schoolcraft. Four of those teams - Bloomingdale, Gobles, Lawrence and Lawton - came from Al-Van League. Two schools - Marcellus and Schoolcraft - left the St. Joseph Valley League to join the new venture. The final school - Decatur - came from the Red Arrow Conference.
Schoolcraft was the first school to depart from the SAC, returning prior to the 1973-74 school year to the SJVL. Martin applied to join the league and began play in 1973. The Clippers came from the Allegan-Ottawa League (A-O).
League membership remained stable with seven teams until Fennville - part of the West Michigan Athletic Association - applied to become the eighth member. The Blackhawks began SAC conference play in 1988-89.
The conference remained at eight members for 15 years until 2003, when four schools joined. Hartford, Watervliet and Bangor - all from the Red Arrow Conference - and Saugatuck (formerly of the OK-Silver Conference) were the newest members. At that point, the SAC changed its format to two divisions - North and South.
A major expansion happened 12 years later. Eight schools from three area conferences became a part of the SAC. When the former Kalamazoo Valley Athletic Association (KVAA) disbanded, six schools applied to the SAC - Constantine, Delton, Galesburg-Augusta, Kalamazoo Christian, Kalamazoo Hackett, and Schoolcraft. Eau Claire, formerly of the Red Arrow Conference, and Coloma, formerly of the Wolverine Conference, completed the expansion. Once again, the SAC changed its divisional format - this time, forming the Valley, Central and Lakeshore divisions.
In 2017, five teams opted to leave the SAC to be part of the newly-formed Southwest 10 Conference. Those teams were Bloomingdale, Decatur, Eau Claire, Hartford and Marcellus. With the league membership now sitting at 13, the SAC opted for just two divisions - Lakeshore and Valley.
Prior to the 2018 season, Lawrence announced it was leaving the SAC to become a part of the Berrien-Cass-St. Joseph League (BCS). With its departure, only Gobles and Lawton remained from the original seven members of the SAC.
In 2019, Parchment applied to begin SAC play in 2020. The Panthers were formerly part of the Berrien-Cass-St. Joseph League (BCS).
A quartet of teams applied and were accepted as SAC members in 2022. Allegan joined after 70 years in the Wolverine Conference. South Haven, another charter member of the Wolverine, joins after two years in the Berrien-Cass-St. Joseph (BCS) League. Bridgman also comes to the conference as a former member of the BCS. Holland Black River was formerly a member of the Alliance League.
The SAC will consist of three divisions for several sports – baseball, softball, volleyball, boys and girls basketball. The divisions are the Lakeshore (Allegan, Bridgman, Coloma, Fennville, South Haven, Watervliet), the Central (Delton, Galesburg-Augusta, Gobles, Holland Black River, Martin, Saugatuck), and the Valley (Constantine, Kalamazoo Hackett, Kalamazoo Christian, Lawton, Parchment, Schoolcraft). The football divisions are as follows: Lakeshore (Allegan, Coloma, Constantine, Kalamazoo United, Parchment, South Haven, Watervliet) and Valley (Delton, Galesburg-Augusta, Lawton, Saugatuck, Schoolcraft). Bridgman, Fennville, Gobles and Martin play in an 8-man football league. Other sports will consist of one or two divisions, depending on the number of teams participating.