At the beginning of the 20th century, the Bitterroots were covered with majestic western white pine, western larch, western red cedar, Douglas-fir, and grand fir, including trees more than 400 years old. As the railroad built its mainline over these mountains in 1907-09, the Forest Service began harvesting white pine seeds from these hills to reseed other forests. The devastating 1910 fire killed most of the giant trees, and the later accidental introduction of white pine blister rust killed most of the white pine, allowing the much shorter-lived lodgepole pine to spread across this area. These changes had important ecological consequences because western white pine and western larch can survive most wildfires, tolerate drought, and resist root disease, while lodgepole pine begins wasting away between 80 and 100 years of age and becomes susceptible to mountain pine beetle attacks. Most of the lodgepole pine in this valley is now more than 80 years old. Severe wildfires also damaged soil in some parts of the valley, creating shrub fields that are only gradually returning to forest. Along the Route of the Hiawatha, some timber harvest areas that supplied the local economy have been replanted with western white pine, western larch, and other species to restore forest health.