- Oatman David - 12 May 1888
- Olive - 11 Sep 1782, Petersham
- Olive - 27 Apr 1808, Windsor, MA
- Olive - 1846, IA
- Olive - 10 Mar 1876, IL
- Olive - c1840
- Olive Dean - 11 Jan 1817
- Oliver - c1839/40, Ludlow, VT
- Oliver Benjamin - 10 Apr 1871
- Oliver Hammond - 4 Mar 1822
- Oliver S. - ; student in 1908-09
- Ophia - c1868, IA [son] [aka: Otho]*
- Orange Guy - 16 May 1836, VT ["Orin"]
- Orissa - 26 Jun 1809
- Orissa - c1844, VT
- Orlean - 1809, Perry Co., IN
- Orleans - 1849, ?Monticello, IA
- Orlin - 9 Apr 1785
- Orlin - 1862; d c1874
- Orlin -
- Orlo -
- Orlow D - 'Nasau, 5 Jun 1878
- Orlow D. - 7 Feb 1819
- Orpha - 26 Jan 1845, Schuyler Falls, NY
- Orrington M. - c1850, DuRuyter, NY
- Otis - 30 Mar 1879, IL