"United States Census, 1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MNQ2-8VB : 15 August 2017), Albert F Zimmerman in household of Edward Zimmerman, Buckeystown, Frederick, Maryland, United States; citing enumeration district ED 66, sheet 26A, NARA microfilm publication T9 (Washington D.C.: National Archives and Records Administration, n.d.), roll 0509; FHL microfilm 1,254,509.
"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M323-RDR : accessed 9 November 2017), Albert F Zimmerman, Election District 1, Buckeystown (west part), Frederick, Maryland, United States; citing enumeration district (ED) 2, sheet 1A, family 8, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,240,622.
"United States Census, 1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M6QL-CD6 : accessed 9 November 2017), Albert Zimmerman, Buckeystown, Frederick, Maryland, United States; citing ED 54, sheet 11B, line 67, family 326, NARA microfilm publication T625 (Washington D.C.: National Archives and Records Administration, 1992), roll 672; FHL microfilm 1,820,672.