MAC is the nation's largest regional professional association for archivists. Founded in 1972, MAC now has over 1150 individual members. MAC's 177 institutional members include a variety of corporate, government, religious, and university archives, as well as historical societies and other manuscripts repositories and special collections. The MAC region is the thirteen heartland states: Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, Ohio, and Wisconsin. However, MAC has individual and institutional members from over 30 other states and five other nations, and more are always welcome.

http://www.midwestarchives.org/