Tree ring patterns in white spruce (Picea glauca) and Sitka spruce (P. sitchensis) from 6 sites on the Kenai Peninsula, Alaska document a widespread disturbance that killed overstory trees between 1880 and 1920. During this period 18-80% of trees in sampled stands record a ring width release (>2 X increase between consecutive 10 yr means of radial growth) suggesting that surviving understory trees grew rapidly into the overstory. Similar ring width patterns are not present nearby in pure stands of mountain hemlock (Tsuga mertensiana) or in isolated treeline white spruce indicating that the growth releases were not caused by regional changes in climate. The nature and magnitude of the community response to the disturbance resemble the response to the Kenai Peninsula's only historically documented outbreak of spruce bark beetles (Dendroctonus rufipennis) which began in the 1960's. A 1904 description of the forest documenting recently killed overstory spruce and living understory spruce suggests that spruce bark beetles are the probable cause of the earlier disturbance. Wildfire probably initiated these stands prior to 1700, and lethal insect outbreaks have been the dominant disturbance agent in the subsequent fire-free interval.