Ecological and historical information are combined in examining the environmental influence of fire and grazing on rangelands in eastern Oregon through time. Competitive relationships between herbaceous and woody flora in the northern Great Basin are discussed, focusing broadly on the shrubsteppe regions 'of Franklin and Dyrness (1973) but with special reference to the Artemisia/Agropyron association. Impacts of native and domestic grazing animals and of cultural burning are traced from the distant past into recent history. During the Pleistocene Epoch North America supported a wide diversity of large mammals. Toward the end of the Pleistocene, many of these fauna became extinct, perhaps as a result of post-glacial climatic change, perhaps also under the influence of incoming primitive hunting cultures and their broadcast burning practices. Some question exists about the intensity of native grazing in the northern Great Basin during the last few thousand years. Actual levels of bison populations and the duration of their residence in the study area have not been determined. The character of indigenous vegetations, however, indicates that native grazing was relatively light for an extended period primevally. Twenty-four references to native cultural burning at the time of European contact were found in historical journals. Though the antiquity of these customs is uncertain, an analysis of Native American fire myths demonstrates the depth of native cultural perceptions of the relationship between man and fire, and supports the likelihood that fire was used primevally in the northern Great Basin as it was used by aboriginal peoples elsewhere in North America. With the influx of European culture during the 19th century, misapprehensions about fire among whites distorted the influence of native cultural burning. Exotic flora and fauna were introduced, and ecosystems began to change. Large herds of livestock depleted native herbaceous populations. Early irresponsible burning by whites became associated with declining rangeland resources, and efforts toward total fire suppression became incorporated in developing conservation policies. Native woody flora and exotics began to invade open rangeland communities. Climatic flux during the period of European settlement in the northern Great Basin may have exacerbated the impacts of intensified grazing and elimination of burning. Early photographs of rangelands in east-central Oregon were gathered; their dates range from 1880 to the early 1930's. Sites represented in these pictures were re-photographed in 1976. Photo-set comparisons show expansion of western juniper (Juniperus occidentalis) populations into rangeland ecosystems, demonstrating the consequences of cultural disturbances during the last 150 to 200 years.