| Name | Birth Date | Where | Christening | Father | Mother |
| Elva Ober |
28 April 1887 |
Primghar, O'Brien, Iowa |
| Joseph Ober |
Margaret E. Schauver Ober |
| August Oberle |
2 May 1897 |
Grant, O'Brien, Iowa |
| Charles Oberle |
Caroline Clem |
| Jessie O'Brien |
12 February 1883 |
Sutherland, O'Brien, Iowa |
| Dennis O'Brien |
Margaret O'Donal O'Brien |
| Lucile O'Brien |
7 March 1895 |
Sutherland, O'Brien, Iowa |
| Dennis O'Brien |
Margaret O'Donal O'Brien |
| Theressa Marion O'Brien |
7 September 1888 |
Sutherland, O'Brien, Iowa |
| James O'Brien |
O'Donald O'Brien |
| Margritt O'Donnal |
21 September 1880 |
Sheldon, O'Brien, Iowa |
| John Chet O'Donnal |
Cordelia Agnes Dowd O'Donnal |
| Gladys Iras Ogan |
3 May 1895 |
Sanborn, O'Brien, Iowa |
| Ira Ogan |
Angie Benner Ogan |
| Herman J. Ohrt |
2 March 1898 |
Liberty, O'Brien, Iowa |
| Dettef Ohrt |
Cecilia C. Rathjen |
| Linda Matilda Oleson |
13 May 1894 |
Sutherland, O'Brien, Iowa |
| Henry Oleson |
Milla Oleson |
| Minnie Maud Olingen |
12 October 1880 |
Carroll, O'Brien, Iowa |
| John Olingen |
Harriet Blair Olingen |
| Leatha Velma Orr |
15 November 1889 |
Paullina, O'Brien, Iowa |
| Emerson B. Orr |
Susana Lee Orr |
| Alfred Herman Ort |
24 April 1898 |
Sheldon, O'Brien, Iowa |
| Theo Ort |
Annie Langenhorst |
| Mollie May Osborn |
6 February 1881 |
Center, Iowa |
| Wm. Lindsey Osborn |
Emma Jane Hammer |
| Detta Osborne |
18 March 1892 |
Sutherland, O'Brien, Iowa |
| Willie Eugene Osborne |
Etta M. Spencer |
| Lottie Osborne |
18 March 1892 |
Sutherland, O'Brien, Iowa |
| Willie Eugene Osborne |
Etta M. Spencer |
| Otto |
18 November 1893 |
Union Township, Iowa |
| Charlie Otto |
Sally Vornsho... |
