The Black Diamond Conference was created first as a football-only conference in 1949. The original schools were members of the Coal Belt Conference for other sports. The original conference schools were Carterville, Christopher, Elkville, Sesser, and Zeigler.
In 1956, the Black Diamond added Boys' Basketball and the conference became full-time.
Carbondale University High, a charter member of the Coal Belt Conference, joined the conference in 1963 and remained a member until its closure in 1968.
In 1962, Elkville High School Consolidated with Vergennes HS to become Elverado High School and Zeigler High School consolidated with Royalton High School to become Zeigler-Royalton High School.
In 1963, Sesser High School Consolidated with Valier High School to become Sesser-Valier High School.
Trico (Campbell Hill) joined the Black Diamond in 1968 -69 season and won three consecutive BDC Basketball Titles. They left the BDC after the 1970-71 season after failing to start a football program.
Carterville and Christopher left the BDC to join the Southern Illini Conference after the 1973 season and returned in 1975. There was no football race in 1974 and no basketball races in 1974-75 and 1975-76.
Johnston City joined the conference in 1975.
McLeansboro (now Hamilton County) joined for football only in 1990 when Christopher and Zeigler-Royalton combined their football programs.
Cairo and Eldorado joined in 1992 for football only.
Eldorado would later join for girls' basketball and both boys' and girls' track and field in 1992 and girls' volleyball in 1995.
McLeansboro joined the BDC for baseball and both boys' and girls' track and field in 1992 and girls' volleyball in 1995.
The 2003-2004 school year saw the largest single expansion in conference history. Carmi-White County and Fairfield joined from the defunct North Egypt Conference and former member Trico rejoined the conference. Cairo, Eldorado, and Hamilton County became full-time members by joining the conference for all sports.
The conference was divided into two divisions, East and West. The West Division consisted of the original five members Carterville, Christopher, Elverado, Sesser-Valier, and Zeigler-Royalton and new member Trico. The East consisted of five new members Cairo, Carmi-White County, Eldorado, Fairfield, and Hamilton County and current member Johnston City.
The conference also began to crown a champion from each division in Basketball and Volleyball. All other sports have one champion. The Diamond Duels in Basketball puts the 6 teams in each division against each other for Bragging Rights. The Duels have no outcome on Conference Champions.
Recent Years 2004-Present
Cairo High School left the conference at the end of the 2007-2008 school year and Vienna High School joined the conference in the 2008-2009 school year.
Carterville left the BDC at the conclusion of the 2009-2010 school year to join the Southern Illinois River-to-River Conference. With Carterville leaving the conference, the Black Diamond dropped Wrestling as a Conference sport as only 3 schools have wrestling programs.
Chester High School joined the BDC for the 2010-11 school year.
Goreville High School joined the BDC for the 2011-2012 school year as a member of the BDC West Division.
Elverado left the BDC at the conclusion of the 2013-14 school year due to dropping their football program. Elverado joined the South Egyptian Conference.
During the 2014-15 school year, the Conference added Division Play to Baseball and Softball. Vienna competed in the BDC West Division in these sports.
Vienna moved all sports to the West Division for the 2016-17 school year.
Edwards County High School joined the BDC in 2016-17 school year and will compete in the BDC East Division.