Former Gov. Mike Rounds was among those spending Thursday trying to protect their homes. Rounds, who moved into a new home along the Missouri River after leaving office in January, said he has built a berm around his home and covered it with plastic tarps and sandbags.

"We don't know what to expect. This is really uncharted territory. This is almost like a free-flowing Missouri River," Rounds said.

Fort Pierre's Verendrye Museum, a collection devoted to the pioneer and cowboy days, is facing flooding.

"The artifacts that are in there, they're mostly of the homestead and the open range days -- a lot of cowboy heritage in there," said Darby Nutter, president of the museum. "Everything's basically in the condition it was in when the folks stopped using it. It's important that we save that piece of history."

Nutter has rented several storage units and is trying to pack up as many photos and other artifacts as he can to get them to higher ground. Just the humidity from the standing water could be harmful to the museum's collection, he said.

Karen Kern, a Pierre resident whose daughter lives in Rapid City, said everyone is "kind of in shock" over the flood risk.