| Name | # Entries |
|---|---|
| Osterhaus | 1 |
| Oscarson | 1 |
| Oseguera | 1 |
| Opp | 1 |
| Odegard | 1 |
| Ottman | 1 |
| Opdyke | 1 |
| Oppelt | 1 |
| Ohmer | 1 |
| Oliveras | 1 |
| Ostroff | 1 |
| Olavarria | 1 |
| Oregon | 1 |
| Olstad | 1 |
| Otting | 1 |
| Orta | 1 |
| Olinger | 1 |
| Oswalt | 1 |
| Orona | 1 |
| Oropeza | 1 |
| Orcutt | 1 |
| Odum | 1 |
| Obryant | 1 |
| Oney | 1 |
| Ortez | 1 |
| Offutt | 1 |
| Odaniel | 1 |
| Otteson | 1 |
| Otterson | 1 |
| Oberst | 1 |
| Ocker | 1 |
| Oglesbee | 1 |
| Ouimet | 1 |
| Ortuno | 1 |