In 1817 fur trader Joseph La Framboise, Jr., an agent for the American Fur Company, established Fort Tecumseh on what is now La Framboise Island in the Missouri River. The fur trade was highly lucrative and attracted competitors. In 1832, Pierre Chouteau, Jr., a major fur trader from St Louis, replaced that early facility with Fort Pierre Chouteau, a trading post on the west side of the Missouri and north side of the Bad River's mouth. The city of Fort Pierre gradually developed around the trading post. Fort Pierre celebrated its bicentennial in 2017, marking 200 years of continuous permanent settlement at the confluence of the Missouri and Bad rivers.

Bearing a large bony frill and three horns on the skull, Triceratops is one of the most recognizable of all dinosaurs. It was also one of the largest, up to 9 meters (30 ft) long and 12 metric tons (13 short tons) in weight. In 1942, Charles R. Knight painted a mural incorporating a confrontation between a Tyrannosaurus and a Triceratops in the Field Museum of Natural History for the National Geographic Society, establishing them as enemies in the popular imagination.

In 1922, the Rapid City Chamber of Commerce invited the Vatican to move to Rapid City. The Pope did not reply.