Alexander worked mostly in museums and historical centers. He served as director of the
New York State Historical Association at
Ticonderoga and
Cooperstown from 1934 to 1941. He went to Wisconsin, where he served as the director of the Historical Society of Wisconsin from 1941 to 1946. For nearly 30 years, he directed activities as the vice president for interpretation at
Colonial Williamsburg from 1946 to 1972. These were decades of major expansion and change, including the beginning of incorporation of more historical material about the common people, enslaved people and women. Following this, he founded the Museum Studies Program at the
University of Delaware, which he directed from 1972 until his retirement in 1978. Deeply engaged in museum operations, he was elected president of the
American Association of Museums and the American Association for State and Local History. ==Legacy and honors==