Mark Compass began as a frogman for the U.S. Navy and later commanding a few of the ships he had first served upon. He became well known as a capable and courageous captain, as well as a noted nautical investigator. Following his naval stint, Compass was employed as a roving troubleshooter for Penny Steamship Lines. In his capacity as ship's detective aboard the S.S. Nautilus, Compass solved many mysteries on the high seas, as well as preventing crimes on the Nautilus and other vessels in the Penny Steamship Lines fleet. Compass currently lives in semi-retirement in his own personal cabin suite on the Nautilus while sleuthing the occasional seaborne mystery.
- This version of Captain Compass, including all history and corresponding appearances, was initially erased from existence following the collapse of the original Multiverse in the 1985–86 Crisis on Infinite Earths limited series. However the ending of Convergence retroactively prevented that collapse, saving all the alternate realities, though in an "evolved" form. Even though versions of the character may have since appeared, this information does not apply to those versions.
- 76 Appearances of Mark Compass (Earth-One)
- 1 Images featuring Mark Compass (Earth-One)
- Quotations by or about Mark Compass (Earth-One)
- Character Gallery: Mark Compass (Earth-One)