"United States Census, 1870," database with images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MDVP-XL3 : 12 April 2016), Ernest W Derby in household of Charles W Derby, Iowa, United States; citing p. 16, family 102, NARA microfilm publication M593 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 545,912.
"Iowa State Census, 1895," database with images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/VTQW-SMT : 11 March 2018), Ernest W Derby, Muscatine, Iowa, United States; citing p. 496, 1895, State Historical Society, Des Moines; FHL microfilm 1,022,088.
"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/M9LS-314 : accessed 3 July 2018), Ernest W Derby in household of Carl N Derby, Wilton Township (excl. Wilton town), Muscatine, Iowa, United States; citing enumeration district (ED) 115, sheet 5B, family 85, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,240,450.
Find A Grave, database and images (https://www.findagrave.com : accessed 03 July 2018), memorial page for Ernest W. Derby (1868–20 Aug 1900), Find A Grave: Memorial #19344647, citing Oakdale Cemetery, Wilton, Muscatine County, Iowa, USA ; Maintained by Ken Wright (contributor 46790894) .