Wheaton. 1 City (1990 pop. 51,464), seat of Du Page co., NE Ill., a residential suburb of Chicago; inc. 1859. It is a religious center and the headquarters of the Theosophical Society of America. Many evangelical organizations are also based there. Wheaton College is in the city, and two museums are nearby. 2 Uninc. city (1990 pop. 58,300), Montgomery co., central Md., a residential suburb of Washington, D.C. It grew (1860s) around a tavern established there in the early 1700s and was named for Union Gen. Frank Wheaton, who defended nearby Fort Stevens in the Civil War.