1925: The Chamber effectively maintained its promotion of the idea for a St. Lawrence waterway, and enlisted the support of the attorneys general of various valley states to resist the case brought against Chicago's water diversion by Wisconsin in the U.S. Supreme Court in 1925.

The Chamber spent $70,000 of its own funds in 1926 to conduct the first comprehensive expert investigation of the Sanitary District of Chicago. The Chamber presented to the City Council, at its request and without cost to the City, a comprehensive survey of street traffic conditions and suggested remedies. This was the most comprehensive study ever completed about traffic for any city in the world. The Chamber raised $300,000 for storm and flood relief to aid Florida hurricane sufferers, and for the sufferers of flooded districts in southern Illinois this year.

During the 1920's, the Chamber organized the "Secret Six." This group became an internationally famous crime fighting body, and was headed by Chamber President Colonel Robert Isham Randolph.

1930: 1930, the Chamber entered a new, difficult and perilous field of public service. Because of the nature of the emergency existing, it organized its own Committee on Prevention and Punishment of Crime. The Secret Six headed the Committee. This was Chicago's first successful experiment on the part of federated business to meet the underworld face-to-face and abate corruption in public office.

The Chamber helped to insure the successful operation of "A Century of Progress Exposition" in 1933 and 1934. The Chamber's sixteen-page rotogravure tabloid (circulation 8,000,000 copies) was the Exposition's largest single publicity medium. The Chamber sold more tickets than any other group, and its "Public School Day at the Fair" brought the record single-day crowd of more than 600,000 students.

1940: In the early 1940's, the Chamber conducted a series of surveys for the City of Chicago. Notable results were the ordinance that took the public schools out of politics and created the position of General Superintendent of Schools. Another made possible the annual savings to taxpayers of two million dollars through the creation of a centralized City Purchasing Bureau. And a third led to the creation of a permanent police labor detail - the famous Barnes Squad.