The Ionia Volcano is located east of Newcastle, Nebraska. Called "Nebraska's Prairie Volcano" by The New York Times in 1901, the smoking hills were long noted by local Native American tribes. The local Ponca tribe considered the hills sacred.  The Lewis and Clark expedition on August 24, 1804 recorded the geological formation. 
According to the description by Captain Clark, the volcano stood 180–190 feet above the Missouri River when they sighted it. Today, the river has shifted and is nearly one mile away from the bluff. The National Park Service reports that Clark wrote,
[sic] "Those Bluffs appear to have been latterly on fire, and at this time is too hot for a man to bear his hand in the earth at any depth, gret[ clarification needed] appearance of Coal. An emence quantity of Cabalt or a Cristolised Substance which answers its description is on the face of the Bluff." 
According to the National Park Service, the source of the heat was a chemical reaction among the various minerals eroding from the bluff, not volcanic activity. As this mineral combination has since washed away, the bluff is no longer hot.  In 1878, the Missouri River washed away the base of the bluff and, with it, all appearances of volcanic activity. A historical marker describing the "volcano" was erected in Pfister Park in nearby Newcastle.
- (January 6, 2009) "Jim McKee: Ionia Volcano a hot topic in 1800s", Lincoln Journal-Star. Retrieved December 24, 2012.
- (December 6, 1901) " Nebraska's Prairie Volcano", The New York Times. Retrieved 12/23/12.
- "Lewis & Clark on the Missouri National Recreational River", National Park Service. Retrieved 12/23/12.
- Placek, M. (Summer 2006) " Ionia Volcano", Living Here magazine. p 7-11.
- "Ionia" Volcano, Nebraska State Historical Society.
- Ionia Volcano, Nebraska State Historical Society.