than welded tuff. The latter material is much easier to excavate, and as a result, the Pajarito contains many more cliff houses. Both areas, however, contain countless petroglyphs. Most of them have been pecked into the ubiquitous basalt. Europeans founded Santa Fe in 1610. It is likely that use of the Caja del Rio for the grazing of domesticated livestock began shortly thereafter. From the beginning of colonization until the 19th century, subsistence users treated the plateau as common property, and used it for summer grazing and timber harvesting. During the mid-19th century, commercial livestock ranching increased throughout New Mexico. By the 1890s, grazing levels throughout the Territory were as high as 9 million animal units. This overuse, combined with severe droughts in 1891 and 1892, led to the loss of top soils and major vegetative changes. Among the vegetative changes were the replacement of more palatable forbs and grasses by woody shrubs and trees. At the beginning of the 20th century, the Forest Service began to address the problem of degraded rangelands. The new solutions included the reduction of grazing permits and the institution of range improvement programs. In 1935, the government purchased portions of the Caja del Rio Grant and the Majada Grant under the "Land Program" of the Federal Emergency Relief Administration. That acreage forms what is today the Caja del Rio Unit of the Santa Fe National Forest. Range surveys, maps, and a range management plan were completed by 1939. In the same year, the Soil Conservation Service assumed administration of the federal lands pursuant to a cooperative agreement among the Indian Services, Resettlement Administration, and the SCS. Responsibility for management was passed to the Forest Service in 1953. The Caja is now managed as a geographically distinct unit of the Espanola District of the Santa Fe National Forest. This unit consists of approximately 67,197 acres in 2010. The Taos Field Office of the Bureau of Land Management manages additional acreage just outside the forest unit. The Caja del Rio Allotment is now managed as a community grazing allotment. Beginning in 1941, most of the existing allotment improvement were repaired or reconstructed. From 1954 to 1972, the average actual use was 711 permitted cattle. In 2010, the Forest Service allows a maximum of 8,305 animal unit months. That capacity is divided among twelve permittees who graze 492 cow-calf pairs and 28 bulls on ten pastures, in