Relatively frequent surface fires recurred for centuries in ponderosa pine and mixed conifer forests of the Southwest before intensive live stock grazing and active fire suppression by government agencies began. The available evidence suggests that extensive (> 100 ha) stand-replacing fires rarely (if ever) occurred in pure, Southwestern ponderosa pine forests before the middle of the 20th century. Extensive crown fires did occur before 1900 in higher elevation mixed conifer and spruce fir forests in the Southwest, but lower elevation mixed conifer forests burned primarily as surface fires, and stand-opening events were probably of limited size (<100ha) in these forests. Repeat photography and tree-ring records of aspen and conifer ages document the occurrence of 19th century crown fires at relatively high elevations. The anomalousness of recent stand-replacing burns in ponderosa pine and some lower elevation mixed conifer forests — in terms of severity, extent, and impacts on soils — is attested to by: (1) the long-term history of sustained surface fires recorded by fire-scarred trees within stands that have now been completely destroyed by late 20th century that have accumulated for tens of thousands of years; (3) the lack of identifiable "landscape-scars” persisting from the 19th century, such as those created by recent large crown fires (e.g., the La Mesa, Dome, and Cerro Grande fires in the Jemez Mountains); and (4) absence of ponderosa pine recruitment, or very slow rates of recruitment into the large holes created by stand-replacing fires in the Southwest over the past 30 years. 20th century landscape scars created by stand-replacing fires in ponderosa pine and lower elevation mixed conifer are long-lasting legacies of human error in managing these ecosystems. Recovery of forest communities within such burned and eroded landscapes may not occur for centuries or millennia. Fire history data and evidence of extreme hydrologic and geomorphic responses following extensive crown fires provide strong justification for management programs aimed at preventing the future occurrence of these ecological disasters.