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- [S3572] 1880 census, Maine, Oxford county, Year: 1880; Census Place: Hartford, Oxford, Maine; Roll: 484; Page: 170C; Enumeration District: 128 (Reliability: 3).
- [S54152] Death record, Maine, Name: Henry D Knapp Gender: Male Death Date: 4 Jul 1912 Death Place: Canton, Oxford, Maine, USA Father: Wm G Knapp Mother: Cynthia A Ripley (Reliability: 3).
- [S11240] 1900 census, Maine, Oxford county, Year: 1900; Census Place: Hartford, Oxford, Maine; Page: 4; Enumeration District: 0189 (Reliability: 3).
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