Summary: Historical fire regimes in plains grassland and prairie ecosystems of central North America are characterized by frequent fires with return intervals ranging from 1 to 35 years. Frequent fires removed accumulated litter, stimulated native grass production, and impeded establishment and spread of cacti and woody plants. Longer intervals occurred in the northern and western part of the region, where the climate was relatively cooler and drier, respectively, and shorter intervals occurred in warmer areas to the south and in areas with more precipitation to the east. Longer intervals also occurred in areas with dissected topography compared to areas with relatively flat topography. Fires were ignited by both lightning and humans, most often in late spring to summer. Grassland fires typically consume most or all of the standing biomass (i.e., high-severity fires). Mixed-severity fires are more likely where shrubs are present. Growing-season fires may be patchier than dormant-season fires due to more variable fuel moisture. Grazing by large ungulates such as bison may alter fuel continuity and result in patchier burns. These once largely continuous grasslands have been fragmented and altered by human settlement, and most of the land has been converted to cropland and rangeland. Therefore, historical fire regimes are no longer functioning, although many grasslands are managed with frequent prescribed fires in spring.