The league was formed in 1976 when a number of new high schools opened up in the previous year.
The formation of the league was to promote athletics and to cut down on travel time and costs.
The league operated under the auspices of the New Jersey State Interscholastic Athletic Association (NJSIAA), the statewide organization for high school sports.
NOTE: Sussex Tech was an Associate Member The SCIL offered a total of 21 sports (12 boys; 9 girls).
In the sport of swimming, Wallkill Valley and Sussex Tech competed as one team known as Wall-Tech.