Formed in 1927 and ending competition in 1997, its membership consisted of small schools located in the southernmost counties of the state along the Wisconsin-Illinois border.
The State Line League was formed in 1927 by eight small high schools in south central Wisconsin: Argyle, Belleville, Blanchardville, Brodhead, Hollandale, Juda, Monticello and New Glarus.
[11] Five years later, South Wayne was merged with Gratiot to form Black Hawk High School, which remained in the State Line League after consolidation.
[12] In 1970, Parkview (formerly Orfordville) High School would leave the State Line League to join the Central Suburban Conference.
[15] Membership in the State Line League remained stable for the rest of its existence with the exception of two schools leaving the conference.