Wood Mountain, elev 1000 m, is located about 135 km southwest of Moose Jaw, Sask, near the Forty-Ninth Parallel. It is underlain by sedimentary rocks that were not eroded by downcutting rivers because of their position between drainage systems. Flat-topped hills, dissected by coulees, rise some 400 m above the surrounding prairie. Métis settled on the slopes of Montagne de bois in 1870, building houses from the plentiful poplar trees. In 1871 the HBC trading post at Wood Mountain became the prairie depot of the Boundary Commission. Use of the area by whisky runners and horse thieves prompted the NWMP to purchase the depot in 1876 and maintain a post until 1918. Over 5000 Dakota Sioux and their leader, Sitting Bull, took refuge in this area after the Battle of the Little Bighorn in 1876. A provincial historic park was established in 1965. The only known sources of helium in Canada exist around Wood Mountain and Swift Current.