| File # | Defendant | Plaintiff | Year |
| 0483 | Oakley, F. W. et al. | Brown, Phillip E. | 1880 |
| 0852 | O'Brien, James | Hanchett, Luther | 1857 |
| 02466 | O'Brien, James et al. | Mason, Lyman H. | 1858 |
| 03735 | O'Brien, James et al. | Wilson, John | 1857 |
| 01063 | O'Brien, P. J. et al. | Commercial Bank | 1892 |
| 03742 | O'Brien, Patrick | Warder, B. H. | 1879 |
| 0967 | Obush, Frank &c. | Coon, D. R. et al. | 1884 |
| 01218 | O'Connell, Daniel | Dorched, Jacob | 1880 |
| 01177 | O'Dell, Mary | O'Dell, Jacob G. | 1846 |
| 0493 | Ogden, John | Bousier, John | 1859 |
| 02274 | Ogden, John et al. | Munn, Herman | 1859 |
| 02724 | Ogden, John et al. | Ogden, Francis | 1864 |
| 04209 | O'Keefe, Anastasia | Zinda, Joseph et al. | 1884 |
| 01501 | O'Keefe, Michael et al. | Grooms, Thomas | 1883 |
| 02641 | O'Keefe, Michael et al. | Nazroe, Henry J. et al. | 1859 |
| 04374 | Okray, John | Storck, Charles | 1900 |
| 02746 | Oles, Josephine | Oles, Wm. H. | 1872 |
| 02721 | Oles, William | Oles, Margaret | 1879 |
| 04292 | Olson, Carl | Bostwick, U. D. | 1859 |
| 02725 | Olson, Oliver | Olson, Anna | 1877 |
| 01408 | Omernick, Frank et al. | Ford, John | 1889 |
| 0989 | Ormsby, John H. et al. | Corrill, J. W. | 1863 |
| 01433 | Orrilmot, Joseph et al. | Grant, Horace | 1858 |
| 0162 | Osowski, Thomas et al. | Zimmer, Charles | 1891 |
| 0501 | Oster, Geo. E. &c. surety on appeal for Eau Pl | Brown, Samuel | 1883 |
| 01077 | Oster, Geo. E. et al. | Curran, Henry | 1883 |
| 03251 | Oster, George E. | Shekell, William | 1878 |
| 02303 | Oster, George E. et al. | McDonald, John R. | 1888 |
| 04347 | Oster, Louise M. | Atwell, V. P. | 1904 |
| 02745 | Ostrander, Henry | Ostrander, Lucinea | 1873 |
| 04394 | Ostrowski, Dorothea et al. | Polak, Rozalija | 1916 |
| 03466 | Ouellett, Hubert et al. | Sylvester, Joseph | 1860 |