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The forest-sagebrush ecotone is characterized by a more arid climate than forested regions; therefore, establishing fire histories using traditional methods (e.g. fire-scars from trees, charcoal in lake sediments) is problematic. This study uses radiocarbon dating of charcoal preserved in alluvial deposits to reconstruct a record of fire and geomorphic response in southwestern Idaho. Samples indicate three primary periods of fire-related activity: 4400-4000, 2000-1400, and 650-400 cal. yr BP. Charcoal macrofossil identification and comparison with other regional records indicate this area has likely alternated between a ’fuel-limited’ system (fires limited by lack of fuels), and a ’moisture-limited’ system (fires limited by too much moisture) with changes in Holocene climate. Over the past similar to 2000 yr, samples from this site indicate most fires occurred during wetter times than the record average. During overall wetter periods, (e. g. ’Little Ice Age’ (LIA); 600-100 cal. yr BP) tree density may have increased, and fires occurred during intervals of relative drought. During times of prolonged drought (e. g. ’Medieval Climate Anomaly’ (MCA); 1025-650 cal. yr BP) fire was recorded during a wetter interval. After similar to 600 cal. yr BP, fire activity was similar to alluvial charcoal records of low-intensity fires in a nearby ponderosa pine-dominated drainage, and sagebrush is common in charcoal samples. Both the ponderosa site and the Wood Creek site show low fire activity in similar to 6500-5000 cal yr BP; climatically, similar to 7-5 ka appears to correspond with regional records of drought. This work provides a unique record of fire in a semi-arid ecotone where (1) few records exist because of the paucity of dating sites, and (2) climatic sensitivity is likely enhanced.