The EOJHL was founded in 1966 as the Rideau-St. Lawrence Junior Hockey League. Through a merger with the Upper Ottawa Valley Junior Hockey League and the folding of the Lanark-Renfrew Junior "C" Hockey League, the league has grown to 22 different teams. The EOJHL is the biggest Junior "B" league in all of Canada and is the only Junior "B" league in the Ottawa District Hockey Association.

The EOJHL is broken up into two traditional conferences that operate separately of each other. Each conference has two divisions. Each conference has its own President and each one operates under variable rules allowed by the ODHA. Each division plays off to declare its own champion, after which the four champion teams play for the Metro/Valley Conference Championship and Rideau/St. Lawrence Conference Championship. The winner of these two championships play in a best-of-7 series for the D. Arnold Carson Memorial Trophy, the EOJHL crown.

The Metro - Valley Conference consists of the Metro Divison and the Valley Division.

The Clarence Castors, Gatineau Mustangs, Metcalfe Jets, Ottawa West Golden Knights and the Ottawa Junior Canadians make up the 5 team Metro Division.

The Almonte Thunder, Arnprior Packers, Perth Blue Wings, Renfrew Timberwolves, Shawville Pontiacs and Stittsville Royals make up the 6 team Valley Division.

The Rideau - St. Lawrence Conference consists of the Rideau Division and the St. Lawrence Division.

The Athens Aeros, Brockville Tikis, Gananoque Islanders, South Grenville Rangers and the Westport Rideaus make up the 5 team Rideau Division.

The Akwesasne Wolves, Alexandria Glens, Casselman Vikings, Char-Lan Rebels, Morrisburg Lions and the Winchester Hawks make up the 6 team St. Lawrence Division.