PS Keystone State (also spelled Key Stone State) was a wooden-hulled American paddle steamer in service between 1849 and 1861. She was built in 1848 in Buffalo, New York, by Bidwell & Banta for ship-owner Charles M. Reed of Erie, Pennsylvania, and operated as part of his "Chicago Line". A luxuriously furnished palace steamer, she operated between Buffalo and Chicago, Illinois, while also making stops at various other ports. She was built for the passenger and package freight trade, frequently carrying both wealthy passengers and European immigrants who desired to settle in the Midwestern United States. Due to the Panic of 1857, Keystone State and several other paddle steamers were laid up. When the American Civil War began in 1861, she was refurbished, and put back into service.

On November 8, 1861, Keystone State left Detroit for Milwaukee, Wisconsin, under the command of Captain Wilkes Travers. Although her cargo manifest listed her cargo as farm machinery, it was rumored that this was a cover for military supplies and gold. She was last seen off Port Austin, Michigan, struggling in a storm, and eventually sank with the loss of all 33 people on board. Keystone State's fate was unknown for over a week, until pieces of wreckage washed ashore.