Rock Mary, Rock formation in Caddo County, Oklahoma, United States

Rock Mary is a low rock formation in the breaks of a creek in Caddo County, Oklahoma, southeast of Hinton. It sits below the level of the surrounding prairie, so it cannot be seen from a distance, though Captain Randolph Marcy chose the hill as a landmark for its prominence on the southern trail to California. A spring once lay just southeast of its foot, with wood available nearby.

This rock formation was first documented during Captain Randolph Marcy's 1849 expedition and named after Mary Conway, a woman who traveled with California-bound pioneers. The landmark served as a key navigational reference point along early westbound travel routes through Oklahoma Territory.

Two plaques placed by the Oklahoma Historical Society in 1960 stand at the site. The lower one records the naming on May 23, 1849 by Lieutenants J.E. Simpson and M.P. Harrison; the upper one marks where they unfurled the American flag on the crest. The name honours Mary Conway, a 17-year-old emigrant travelling to California with her family.

This rock formation sits on private property south of Interstate 40 and is accessed via County Road E1060 near Hinton. Visitors should verify access permissions in advance since the site is privately owned and not always open to the public.

The two plaques at Rock Mary were placed by the Oklahoma Historical Society in 1960. The lower one records the naming on May 23, 1849; the upper one marks where Lieutenants J.E. Simpson and M.P. Harrison unfurled the U.S. flag on the crest that day.