"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MSW9-YS3 : accessed 9 April 2018), Mary J Duncan in household of Charles Duncan, Isabel Township, Fulton, Illinois, United States; citing enumeration district (ED) 21, sheet 1A, family 11, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,240,302.