The impetus for its demise came inadvertently and unknowingly from a member of the neighboring Big Twelve Conference.
At the time, the Big Twelve Conference membership roster included Bloomington, Champaign Central, Danville, Stephen Decatur, Lincoln, Mattoon, Springfield, and Urbana.
Initial discussions were instigated by representatives of Springfield High School to look into the potential feasibility of swapping schools within the two conferences where there was some common city "overlap" (this was present in Bloomington-Normal, Champaign-Urbana, Decatur, and Springfield).
This would allow each conference to align even more tightly geographically, thus increasing rivalries and reducing costs.
Rather than proceed in that direction, the remaining members of the Big Twelve Conference alternatively decided to offer membership to all of the Capitol Conference non-Springfield "overlap" institutions (Champaign Centennial, Decatur Eisenhower, Decatur MacArthur, and Normal Community) plus Rantoul, while jettisoning Springfield.