The recent fire history of Barron Township (18,600 ha) in Algonquin Park was studied by examining historical documents and dating past forest fires using dendrochronological techniques. Lightning is still a major ignition source. Over the 36-year period of 1939-1974, lightning accounted for 48.5% of all fires at a rate of 0.19 fires per year per 10,000 ha. Dendrochronological data show that 16 fires burned during the 225-year presuppression interval from 1696 to 1920 for a mean frequency of 14.1 years. Five major fires (1875, 1864, 1854, 1780 and 1763) each burned at least half of the township with a mean frequency of 45 years. Meteorological data show that drought prevailed across southern Ontario during 1875, when major fires burned in Barron Township and northern Minnesota, supporting the suggestion that severe fire years correspond with periods of subcontinental drought. Similarly, 1864 appears to have been a major fire year in Barron as it certainly was in Minnesota. The recent fire rotation, i.e., the average time required to burn an area equivalent to the size of the study area is about 70 years. Field evidence and increment borings suggest that the present vegetation mostly originated as a consequence of the fire of 1875. Abstract reproduced by permission of The Canadian Journal of Botany.©NRC Canada