On Wednesday evening, a flash flood reportedly hit Bannack State Park west of Dillon, causing so much damage that officials say they've had to cancel Bannack Days.
We talked with the State Park Manager Dale Carlson, who told us he has no idea how much has been damaged, but he knows at least one building is down and some of the boardwalks have been washed out.
Stan Smith, one of the organizers of Bannack Days, also tells us damage is severe.
No one was injured.
Neighbors in the area report well over three-quarters of an inch of rain fell within just minutes.
Carlson told us they're assessing the damage, and will have a better idea Thursday.
Bannack Days, a popular annual event held at the historic ghost town, would have taken place the weekend of July 20.
Smith tells NBC Montana this is the first time Bannack Days have been canceled since they began in 1976.
We are continuing to get the latest information as this story develops, and will post updates here and our Facebook page KTVM 6.