| Surname | First Name | Middle Name | War | Information | Entered Service | Service | Birth | Death | Cemetery |
| Oaks | P. | R | Civil War | Army Confederate Soldier | 1861 | 1865 | 1832 | 1900 | Blairsville |
| Oberline | William | P | Civil War | Army Infantry Co E 148tgh Reg P V Pvt | 9-2-1862 | 6-5-1865 | 14 Nov. 1835 | 20 Aug. 1897 | Pine Grove/Canoe |
| Ogden | George | Hill | Civil War | Army Infantry Co E 11th PVI Pvt wounded at Bull Run | 10-4-1861 | 10-29-1862 | 15 Aug. 1839 | 9 Jan. 1891 | Oakland |
| Ogden | Joseph | Clark | Span Am War | Troop K 6th US Cav Pvt | 1898 | 8 Nov. 1870 | 20 Mar. 1937 | Oakland | |
| O'Harrah | Harrison | Civil War | Army Infantry Co A 206th Reg P V Pvt | 8-28-1864 | 6-26-1865 | 1844 | 1908 | Rowley | |
| O'Kiefe | Michael | Civil War | Army Co F 67th PV Reg Pvt KIA 2 Apr. 1865 | 4-2-1865 | 1833 | 2 Apr. 1865 | Memorial Park | ||
| Oliver | J | Matthias | Civil War | Co G 206th Reg Mil PVI Pvt | 6-30-1863 | 8-17-1863 | 1839 | 1925 | Conemaugh |
| Oliver | James | Civil War | Co I, 46th Reg PVI Pvt | 10-13-1861 | 29 Apr. 1811 | 6 Jul. 1873 | Conemaugh | ||
| O'Neil | Henry | Civil War | Army Infantry Co B 56th Reg PVI 1st Lt | 10-29-1861 | 3-8-1862 | 17 Jan. 1910 | SS Simon & Jude | ||
| O'Neil | John | Civil War | Army Infantry Co B 67th Reg PVI Sgt | 3-11-1865 | 7-14-1865 | 14 Apr. 1836 | May. 1930 | Oakland | |
| Onstott | Virgil | S | WW I | Army SATC ORC Eng 2nd Lt | 1918 | 1897 | 1927 | Edgewood,Saltsburg | |
| Orner | Daniel | J | Civil War | Army Cavalry Co K 67th Reg Cavalry Cpl | 11-4-1862 | 7-14-1865 | 18 Dec. 1836 | 27 Jul. 1921 | Strongstown |
| Orr | George | Kunkle (Kimmel) | Civil War | Army Infantry Co C 57th reg Mil 1863 PV Musician | 7-3-1863 | 8-17-1863 | 1830 | 1900 | Greenwood |
| Ortz | David | Civil War | Army Infantry and artillery, PVt Co A 135th Reg PV 8-14-1862 to 5-24-1863 Co E 5th Reg Art 104th | 8-29-1864 | 6-30-1865 | 15 May. 1840 | 12 May. 1918 | Greenwood | |
| Osborne | Josephus | Civil War | Army Artillery Bty C 1st Art 43rd Reg PV Pvt | 2-17-1864 | 6-29-1865 | 19 Mar. 1831 | 10 Feb. 1912 | St Bernards | |
| Overdorf | Michael | A | Civil War | Army Artillery Battery L 6th Heavy Art 212trh Reg P V Pvt | 8-30-1864 | 6-13-1866 | 1916 | Blairsville | |
| Overdorff | Franklin | Civil War | Army Infantry Co F 55th Reg PVI PVt SCD | 2-13-1864 | 1847 | 4 May. 1910 | Greenwood |
Indiana County, PA