Key Marco, on a shell-work island beside Marco Island in southwest Florida, became one of the most important prehistoric archaeological sites in the eastern United States because a wet muck pond preserved fragile organic materials rarely found elsewhere. Excavated in 1896 by the Smithsonian’s Pepper-Hearst Expedition under Frank Hamilton Cushing, the site yielded more than 1,000 wooden artifacts, including tools, fishing gear, masks, animal heads, and the famed Key Marco Cat. Though dating has remained difficult, the site is linked to the Muspa of the Glades culture. Later excavations revealed a large, socially complex settlement, but the site itself was eventually destroyed by development.