Clayton left to join the Lakeland Conference in 1936,[2] and the conference consolidated into a single division. In 1940, the five smallest schools in the conference (Balsam Lake, Centuria, Luck, Milltown and Webster) joined with Siren to form the Northwest Border Conference.[3] Milltown returned to the Upper St. Croix Valley Conference in 1942,[4] bringing the membership roster back up to six schools. In 1946, Luck followed Milltown out of the Northwest Border Conference to becom the Upper St. Croix Valley's seventh member school.[5]Webster reentered the conference from the Northwest Border Conference in 1953, bringing the total number of schools to eight.[6]
Since Webster joined in 1953, there were relatively few changes to the roster, and the Upper St. Croix Valley Conference maintained an eight-member loop for the remainder of its existence. In 1957, Milltown was merged with two former Upper St. Croix Valley members in the Lakeland Conference (Balsam Lake and Centuria) to form Unity High School in Balsam Lake, and the new school inherited Milltown's place in the conference.[7] Amery left the conference for membership in the Middle Border Conference in 1977[8] and were replaced by Somerset, late of the Dunn-St. Croix Conference.[9]
The Upper St. Croix Valley Conference continued on for seventeen more years before it was disbanded in 1994, and its members were dispersed to other conferences in the area. Four schools (Frederic, Grantsburg, Luck and Webster) became members of the Lakeland Conference,[10] three members (Osceola, St. Croix Falls and Unity)[11] joined the Middle Border Conference and Somerset returned to the Dunn-St. Croix Conference.[12]
