| Year | Date | Historical Events |
| 1917 | Feb 15 | Keel laid down at the Fore River Shipbuilding Co., Quincy, Mass. |
| 1918 | Jan 27 | Launched. |
| | Jul 27 | Commissioned with LT. Oliver M. Read, Jr. in command.
|
| | Nov 2 | O-9 departed Newport, R.I. for European waters, but the termination of hostilities brought the 20-sub force back to the United States.
|
| 1924 | Jun 15 | Proceeding to Coco Solo, C.Z. in 1924, O-9 was reclassified to a "Second Line" submarine during her year there. (Exact date unknown) |
| 1925 | Jun 15 | O-9 returned to operate at New London, CT. |
| 1928 | Jun 6 | O-9 reverted to a "First Line" submarine. |
| 1930 | Jan 15 | O-9 sailed to Portsmouth, NH. (Exact date unknown) |
| | Mar 15 | O-9 returned to New London, CT. (Exact date unknown) |
| 1931 | Feb 15 | O-9 sailed to Philadelphia, PA. for decommissioning. |
| | Jun 25 | Decommissioned at Philadelphia, PA. |
| 1941 | Apr 14 | Recommissioned at Philadelphia, PA. |
| | May 31 | O-9 went to New London, CT. |
| | Jun 19 | O-9 departed New London, CT. with other O-boats for tests off the Isles of Shoals. |
| | Jun 20 | O-9 submerged at 0738 to conduct deep submergence tests, the sub did not surface thereafter but was crushed by the pressure of the water 402 feet below. 33 men lost. |
| | Oct 23 | Struck from the Naval Register. |