In the greater Maricopa County, local government cooperation in the early 1960's resulted in the implementation of the multi-city sewage treatment plant at 91st Avenue. This regional activity occurred prior to federal and state initiatives and incentives for regional planning and cooperation. In 1962, changes in federal policy required more local and state involvement. As a result of changes in the Federal Aid Highway Act, cooperative transportation planning occurred with the creation of the Valley Area Traffic and Transportation Study (VATTS). As part of the federal government decentralization initiatives, federal regions were established to bring federal programs closer to the people and incorporate greater review of federal programs through the Intergovernmental Cooperation Act.
Because of these changing federal policies requiring more local planning and review, and due to the demonstrated success of previous regional efforts, the local governments in Maricopa County formed MAG in 1967 as a nonprofit corporation to act as the vehicle to address areas of common regional interest. At the first meeting of MAG, the consensus of the Regional Council was that the areas of water, air pollution and solid waste disposal were of primary concern. It was also agreed that there was a need for the standardization of building materials and for public works specifications. In addition, the transportation planning efforts begun with VATTS were incorporated into the scope of MAG's work. Several key events in the early history of MAG are outlined below:
- Regional cooperation was encouraged by success of multi-city sewage system in the early 1960s.
- The 1962 Federal Aid Highway Act required regional transportation planning, which resulted in the formation of the Valley Area Traffic and Transportation Area Study (VATTS) on March 12, 1965.
- The 1965 Federal Housing Act Amendments and 1966 Metropolitan Development Act provided legal and financial impetus for a full-fledged regional agency.
- MAG was formed in 1967 by concurrent resolutions from its member agencies to foster regional cooperation and to address regional problems.
- VATTS was incorporated into MAG in 1967.
- Executive Order 70-2 established six Planning Districts in Arizona in 1970.
- MAG designated as the Metropolitan Planning Organization (MPO) by the governor in 1973.
- MAG designated as the Water Quality Planning Agency by the governor in 1975.
- MAG designated as the Lead Air Quality Planning Agency by the governor in 1978.
- MAG designated as the Solid Waste Planning Agency in 1979.