| Last Name | First Name | Event* | Day | Month | Year | Publication Date | Wife | Husband | Mother | Father | Locaton of Event | ||
| Oagub | Susan A. | m | 31 | Jul | 1857 | 22 | Jul | 1857 | Bowne, Alexander | Deer Creek Crossing, Nevada County | |||
| Oague | Miss Melina A. | m | 12 | Sep | 1857 | 10 | Sep | 1857 | Stewart, Samuel | Yuba County | |||
| O'Bannor | Mary Elvira | d | 5 | May | 1857 | 2 | May | 1857 | O'Bannor, Mary Anne | O'Bannor, Dr. | Live Oak City, Sacramento County | ||
| Obray | Thomas | m | 17 | Oct | 1857 | 2 | Aug | 1857 | Brenchley, Caroline | Salt Lake City | |||
| O'Brien | Miss Maggie | m | 9 | Oct | 1857 | 4 | Oct | 1857 | D'Arcy, Count J. | San Francisco | |||
| O'Brien | son | b | 12 | Oct | 1857 | 4 | Oct | 1857 | O'Brien, John | Michigan Bar, Sacramento County | |||
| O'Callaghan | Major H. H. | m | 2 | Jul | 1857 | 14 | Jun | 1857 | McPherson, Miss Caroline J. | Sonoma | |||
| Ochs | Louis | d | 26 | May | 1857 | 24 | May | 1857 | San Francisco | ||||
| O'Connor | Miss Mary | m | 25 | Apr | 1857 | 24 | Apr | 1857 | Cochran, Thomas | Sacramento | |||
| O'Connor | son | b | 21 | Nov | 1857 | 20 | Nov | 1857 | O'Connor, Jr., Daniel | Marysville | |||
| O'Connor, Jr. | Daniel | m | 12 | Feb | 1857 | 8 | Feb | 1857 | Fitzpatrick, Miss Margaret | San Francisco | |||
| Odam | Miss Lucy | m | 9 | Apr | 1857 | 8 | Apr | 1857 | Feran, Henry | Sacramento | |||
| Oden | Mary Jane | m | 13 | Jul | 1857 | 8 | Jul | 1857 | Taylor, Wm. | San Francisco | |||
| Odeneal | T. H. B. | m | 4 | Jun | 1857 | 29 | Apr | 1857 | Coyle, Miss Eliza F. | Oregon | |||
| O'Donnell | dau | b | 1 | Jun | 1857 | 22 | May | 1857 | O'Donnell, J. | Vallecito | |||
| Offrerding | Dr. | d | 29 | Aug | 1857 | 26 | Aug | 1857 | Sacramento | ||||
| Ogilen | Fannie Bensley | d | 19 | Jun | 1857 | 15 | Jun | 1857 | Ogilen, Mary | Ogilen, Frederick | Napa City | ||
| Ogilvie | John | d | 27 | Jul | 1857 | 25 | Jul | 1857 | San Francisco | ||||
| Ogle | Antone | m | 31 | Aug | 1857 | 16 | Aug | 1857 | Fried, Miss Margurietta | Yreka | |||
| O'Hara | James Wesley | d | 12 | Aug | 1857 | 7 | Aug | 1857 | Marysville | ||||
| O'Hara | John | d | 1 | Aug | 1857 | 29 | Jul | 1857 | San Francisco | ||||
| O'Hara | Mr. | d | 14 | Aug | 1857 | 13 | Aug | 1857 | Santa Cruz | ||||
| O'Hara | Mrs. Eliza | m | 16 | Jul | 1857 | 25 | Jun | 1857 | Vandepool, John | Benton County | |||
| Ohmeyer | Miss Ellen | m | 8 | Dec | 1857 | 5 | Dec | 1857 | Auberlin, Mr. August | San Francisco | |||
| Oldfield | Miss Mary J. | m | 15 | Apr | 1857 | 11 | Apr | 1857 | Lambert, Geo. G. | San Francisco | |||
| Oldham | J. F. | m | 29 | Oct | 1857 | 25 | Oct | 1857 | White, Ellen | Nevada | |||
| Olendorff | Emily C. | d | 15 | Dec | 1857 | 5 | Dec | 1857 | Olendorff, Dr. | Shasta | |||
| Olinda | Mr. Van | d | 11 | Jul | 1857 | 9 | Jul | 1857 | Butte City, near Jackson | ||||
| Olinger | Mary R. | m | 6 | Nov | 1857 | 28 | Oct | 1857 | Cummings, Wm. | Pajaro, Santa Cruz County | |||
| Oliver | Catherine | d | 25 | Aug | 1857 | 21 | Aug | 1857 | Oliver, John B. | San Francisco | |||
| Oliver | Mary Cecilia | d | 14 | Oct | 1857 | 10 | Oct | 1857 | Oliver, Bridget M. E. | Oliver, Dennis J. | San Francisco | ||
| Oliver | William T. | m | 16 | Jun | 1857 | 29 | Mar | 1857 | Lovelorn, Nancy J. | Ogden City, Utah | |||
| Oliver | dau | b | 15 | Apr | 1857 | 14 | Apr | 1857 | Oliver, John B. | San Francisco | |||
| Olmstead | dau | b | 21 | Apr | 1857 | 16 | Apr | 1857 | Olmstead, Wm. T. | Weaverville | |||
| Olmstead | Myrtle A. | d | 19 | Oct | 1857 | 12 | Oct | 1857 | Olmstead, Rachel A. | Olmstead, James P. | Iowa Hill | ||
| O'Mara | son | b | 19 | Aug | 1857 | 17 | Aug | 1857 | O'Mara, Michael | Sacramento | |||
| O'Mearu | Cornelius J. | d | 10 | Sep | 1857 | 8 | Sep | 1857 | San Francisco | ||||
| O'Neal | Col. J. C. | d | 1 | Mar | 1857 | 8 | Feb | 1857 | Rivas | ||||
| O'Neal | John | d | 16 | Dec | 1857 | 12 | Dec | 1857 | Stockton | ||||
| O'Neal | John | m | 19 | Aug | 1857 | 11 | Aug | 1857 | Malarky, Miss Eliza | Jamestown, Tuolumne County | |||
| O'Neil | Edward | d | 27 | Apr | 1857 | 24 | Apr | 1857 | San Francisco | ||||
| O'Neill | dau | b | 23 | Sep | 1857 | 21 | Sep | 1857 | O'Neill, Edward W. | Sacramento | |||
| O'Neill | Miss Sarah | m | 27 | Nov | 1857 | 1 | Nov | 1857 | Kelly, Mr. Dennis | O'Neill, Mr. J. | Honolulu | ||
| Onfray | Michael L. | m | 15 | Apr | 1857 | 11 | Apr | 1857 | Bachelder, Miss Juliette | San Francisco | |||
| O'Niel | Margaret | d | 25 | Jun | 1857 | 22 | Jun | 1857 | San Francisco | ||||
| Orarmuno | dau | b | 18 | Mar | 1857 | 8 | Mar | 1857 | Orarmuno, Senor Mateo | Downieville | |||
| Ordway | Robert | m | 2 | Sep | 1857 | 30 | Aug | 1857 | Gabbs, Cecelia | San Francisco | |||
| Oretega | Donna Feliciana De Ramonsita | m | 31 | Mar | 1857 | 11 | Mar | 1857 | Hitt, Robt. | San Luis Obispo | |||
| Orr | Jane | m | 13 | Oct | 1857 | 8 | Oct | 1857 | Twine, Elias | Shasta | |||
| Orr | Miss Eliza S. | m | 14 | May | 1857 | 12 | May | 1857 | Wethered, Thos. | San Francisco | |||
| Orr | Wm. M. | d | 23 | May | 1857 | 20 | May | 1857 | Marysville | ||||
| Orrick | twins son & dau | b | 23 | Nov | 1857 | 21 | Nov | 1857 | Orrick, Mr. | American township, Sacramento County | |||
| Osborn | Miss Sarah A. | m | 2 | May | 1857 | 23 | Apr | 1857 | Neville, John M. | San Francisco | |||
| Osborn | Mrs. Sarah A. | m | 5 | May | 1857 | 22 | Apr | 1857 | Neville, John M. | San Francisco | |||
| Osborne | Wm. G. | m | 28 | Jun | 1857 | 4 | Jun | 1857 | Morgan, H. Jane | Olympia, Oregon | |||
| Ostock | George | m | 14 | Nov | 1857 | 5 | Nov | 1857 | Blake, Mrs. Mary W. | San Jose | |||
| O'Sturdivant | Robt. | m | 9 | Sep | 1857 | 3 | Sep | 1857 | Hutchinson, Lacretia M. | Oakland | |||
| O'Sullivan | son | b | 21 | Sep | 1857 | 18 | Sep | 1857 | O'Sullivan, C. D. | San Francisco | |||
| Otis | Miss Anna | m | 5 | Aug | 1857 | 3 | Aug | 1857 | Laird, George P. | San Francisco | |||
| Otto | John H. | d | 21 | Feb | 1857 | 25 | Feb | 1857 | Otto, Henry | Yreka | |||
| Overlin | S. I. | m | 7 | Sep | 1857 | 27 | Aug | 1857 | Sackett, Rhoda L. | Suisun | |||
| Owen | Mr. Eben | m | 17 | Sep | 1857 | 30 | Jul | 1857 | Dale, Miss Mary W. | Portsmouth, N. H. | |||
| Owens | Miss Lucinda | m | 13 | Mar | 1857 | 26 | Feb | 1857 | Harden, Wm. J. | San Francisco | |||
| Owens | Mr. Owen | m | 18 | Dec | 1857 | 14 | Dec | 1857 | Robbins, Miss Iciphenie C. | Marysville | |||
| Owsley | Lewann Montgomery | d | 24 | Mar | 1857 | 5 | Mar | 1857 | Owsley, Maria | Owsley, Wm. M | Scott's Valley, Napa County | ||
| Oxendine | Miss Jane | m | 29 | Apr | 1857 | 26 | Apr | 1857 | Haridson, John | Stockton |
* Event (b m d div) = birth, married death, divorce