History of COSC

The idea of a national association of state chambers of commerce was originally discussed at a roundtable session on November 1, 1923, at Hotel Gibson in Cincinnati, Ohio. Among the states represented at that meeting were Connecticut, Massachusetts, Missouri, Wisconsin, Florida, Oregon, Pennsylvania, Illinois, Iowa, Ohio, Indiana, and the Chamber of Commerce of the United States. The first annual meeting of COSC, then called the National Association of State Chambers of Commerce, was held on October 9, 1924, in Pittsburgh, Pennsylvania.

A detailed history of the organization is available on the Wiki.