Spotted knapweed is native to Europe.
It is believed that it entered Canada in 1893 and is now distributed through out many portions of Canada and the United States. Estimates show that Spotted knapweed now infests nearly two million acres in Montana. It probably found its way to Park County via the Northern Pacific Railway and the associated construction equipment that the railroad used for crushing and hauling rock at the Merriam Quarry just south of Emigrant. The firm that had the rock contract worked the Merriam site and a site near Clinton, Montana which is in the heart of Montana's Knapweed. The infestation in Park County has generally radiated from the quarry with the help of man and machine.