The Tri-State Treaty Commission, the predecessor organization of the Interstate Environmental Commission was organized.

Interstate Sanitation Commission formed. On January 24, 1936 the Tri-State Compact was formally signed by New York and New Jersey.

ISC performed first inspections. The first inspections completed by the Commission were made for the purpose of sampling and analyzing the sewage treatment plant influent and effluent for the purpose of determining the effectiveness of the treatment and whether it is complying with the terms of the Interstate Compact.

On February 1st, 1936 The Commission established its first office at 60 Hudson Street.

Connecticut joined the commission
(September 17, 1941)

At least 21 sewage treatment plants were completed and placed into operation between 1952 and 1956. (Plant sites included, Owl’s Head, Oakwood Beach, Hunt’s Point, Rockaway Port Washington and Glen Cove in New York; Linden Roselle, Bayonne, and Woodbridge in New Jersey; and Fairfield, New Haven, and Milford in Connecticut.

ISC completed a survey of upper New York Harbor with the Army Corps of Engineers. IEC also completed monitoring surveys on the Arthur Kill, due to the location of the Kill and its exposure to great amounts of pollution from the chemical and petroleum industry.

As a result of a tug boat strike, three regional wastewater treatment plants became overfilled with sludge, resulting in thousands of tons of sludge being discharged directly into District waters.

The first East River monitoring survey included the East River and Long Island sound; including areas around Little Neck Bay and Eastchester Bay that IEC still monitor today.

ISC adopted standards for effluent as well as ambient water. ISC was designated as the official planning and coordinating agency for the NJ-NY-CT air quality control region.

ISC updated standards for the amount of oxygen which must be present in the water, allowable solids and "a more ridged bacterial standard." They reclassified the waters of the IED – these classes are still in use today. About 106 water pollution control projects were completed, under construction, or in the planning stage.

In October 1987, the Commission acquired its own research vessel, the R/V Natale Colosi, named after IEC’s former Chairman, for conducting ambient water quality surveys.

In October 1994, the Commission moved its laboratory from Columbus Circle, to the City University of New York’s College of Staten Island campus, where it remains today.

On October 27, 2000 the President of the United States signed the Bill containing the language that changes the name of this agency from the Interstate Sanitation Commission to the Interstate Environmental Commission—bringing the Commission into the 21st Century with a name that more accurately reflects the Commission’s mandates, mission, and responsibilities that embrace a broad range of programs beyond wastewater.

The laboratory obtained certification through the National Environmental Laboratory Approval Program.

The laboratory moved its headquarters to the laboratory facility located on the City University of New York’s College of Staten Island campus.