"United States Census, 1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MXJR-TB5 : accessed 25 July 2015), Jan Jonkman, Onarga, Iroquois, Illinois, United States; citing enumeration district 138, sheet 300C, NARA microfilm publication T9 (Washington D.C.: National Archives and Records Administration, n.d.), roll 0214; FHL microfilm 1,254,214.