Mann Mound is a Native American earthwork in southwestern Ohio near Jacksonburg and the second largest surviving mound in Butler County. Associated with the Adena culture, it stands about 20 feet high and roughly 540 feet in circumference. Its archaeological importance became clear in November 1868, when quarrying for gravel exposed multiple limestone burial vaults stacked through the mound’s center, each containing a seated skeleton. Eight skeletons were removed and sent to the Smithsonian Institution, helping identify the mound’s cultural origin. Despite damage from that excavation, the site remained significant, was recorded in an 1879 survey by J.P. MacLean, and was listed on the National Register of Historic Places in 1971.