- Obsidian is found in volcanic areas where the magma is rich in silica and lava has cooled without forming crystals, creating a black glass that can be honed to an exceptionally thin edge.
- Obsidian was first quarried from this cliff for toolmaking more than 11,000 years ago and gradually spread along trade routes from western Canada to Ohio.
- Unlike most obsidian, which occurs as small rocks strewn amid other formations, Obsidian Cliff has an exposed vertical thickness of about 98 feet (30 m).
- It is the United States’ most widely dispersed source of obsidian by hunter-gatherers.
- Obsidian Cliff is the primary source of obsidian in a large concentration of Midwestern sites, including about 90% of obsidian found in Hopewell mortuary sites in the Ohio River Valley (about 1,850–1,750 years ago).
About 90% of the Obsidian Cliff plateau burned in 1988. Although the fire did not affect the appearance or condition of the cliff face, it cleared the surface and most of the lodgepole pine overstory, creating optimal conditions for archeological surveys. The surveys have added substantially to knowledge about how and where obsidian was mined from the bedrock and collected as cobbles deposited within the overlying glacial till. The site was designated a National Historic Landmark in 1996.
The kiosk at Obsidian Cliff, constructed in 1931, was the first wayside exhibit in a US national park. It was listed on the National Register in 1982.