A researcher has examined scientific and historical literature for reports of wildfires occurring between 1776 and 1900. George E. Gruell of the U.S. Forest Service found 145 accounts of fires documented by 44 observers. Most accounts described fires in progress. Others referred to burned areas that were encountered, while a few simply described regional fire occurrence. Ten were recorded by Lewis and Clark.
The approximate location of each fire was plotted on the map above. The majority of these reports were made along principal travel routes. Documentation is lacking over large areas where travel was infrequent or not mentioned by the journalist.
Mr. Gruell wrote:
Indian-set fires were apparently the primary ignition source over wide areas at lower and middle elevations. Of the 145 references to fires, 41 percent were attributed to Indians; 5 percent were attributed to non-Indians, and 54 percent made no mention of ignition source. Very likely some lightning fires were inaccurately attributed to Indians, and the fires of unknown origin were caused by both Indians and lightning. Nevertheless, the available record does indicate that Indian-set fires were common.