Wilderness areas are primarily set aside to protect natural ecosystems and processes. However, most protected areas have a long history of native peoples' land use predating their protection. The general paucity of evidence in the form of historical records, in combination with romantic views of native peoples' effects on nature, often leads to their impact being underestimated. The analysis of culturally modified trees in protected old-growth forests has increasingly been recognised as an important tool for analyzing long-term trends in native peoples' land use. The aim of this study was to gather evidence of native peoples' use of the ponderosa pine forest in the South Fork Valley of the Bob Marshall Wilderness area, Montana, USA, by analyzing trees with bark-peeling scars (the result of past inner bark collection) and then using written historical and ethnographic records (as far as possible) to corroborate the information obtained. The method used (peeling) to collect the inner bark did not kill the trees, thus leaving live trees with characteristic scars, which can be dated by using dendrochronology. We studied 138 bark-peeling scars on trees at four sites within this wilderness area, and the results show that Native American tribes visited the area regularly in the spring to collect ponderosa pine inner bark at specific sites. The majority of the scars were from the 1800s, the oldest scar was from 1665 and the youngest from 1938. Between 20% and 25% of the old ponderosa pines at the studied sites had such scars. These results indicate that analysis of culturally modified trees can provide a detailed temporal and spatial record of the presence of native peoples in a remote wilderness area and can be used to analyze important aspects of historic human land use.