The Civil Service Technical Guild was established in 1937 to represent engineers and architects employed by the City of New York. It began as Council 6 of the Civil Service Forum by three engineers, Henry F. Cunningham, William F. Elliot, and George Ellenoff. The first activity of the organization was a protest against the contracting out of public works by the City to private firms. The union mobilized 300 engineers who went to the state capitol to lobby for the passage of the Buckley Law, which proposed repealing from the New York City charter a provision which actually required contracting out of large projects. After the passage of the Buckley Law, the Guild's membership increased by approximately 2,000 new members, representing 25 city departments (adding chemists and technical inspectors, among others).

In 1948 the Guild disaffiliated from the Civil Service Forum and was independent until 1951 when it merged with the Government and Civic Employees Organizing Committee (GCEOC) of the CIO, and finally with the American Federation of State, County and Municipal Employees, District 37 after the AFL-CIO merger in 1956. One of the key figures in the founding of the Guild was Philip Brueck, who was elected its President in 1938 and held that post for almost twenty years. Building upon the passage of the Buckley Law, Brueck's political strategy for the Guild was to lobby for legislation rather than to use strikes. By the 1960s the Guild had won the right of collective bargaining and over the years won for its members improved salaries, medical and dental benefits, Social Security and long-term disability insurance.