Extensive areas of the semidesert grassland of the Southwest are dominated by creosotebush [Larrea tridentata (DC) Coville], mesquite [Prosopis julifiora (Swartz) DC], and tarbush (Flourensia cernua DC). Mesquite occurs on 93,000,000 acres; creosotebush is present on 46,500,000; and tarbush occurs on 13,250,000 acres (Platt, 1959). Although the species are indigenous, they have invaded large areas in the past 100 years. Some areas invaded by tarbush still have a good understory of grass. However, loss of forage production occurs in early stages of mesquite invasion (Norris, 1950). In creosotebush-dominated areas, forage production is negligible (Gardner, 1951). The productivity of the rangeland greatly influences the economy of the Southwest. Therefore, it is important for the rancher to conserve and, where necessary, improve the range resource. Some knowledge of original vegetation conditions is essential in properly evaluating the potential of various sites. Much has been written about the semidesert grassland, including quotations from many early travelers. Some authors have based general assumptions on these quotations. However, the quotations are difficult to evaluate properly. In making their observations, many early travelers were influenced by the seasons and by their personal emotions. Furthermore, very few of the areas described by early travelers can actually be relocated for present-day comparisons. This study aims to show the degree of encroachment of brush on the study area and also the nature of the invasion on various soil types. Vegetation surveys of 1858, 1915, 1928, and 1963 were compared. Factors possibly responsible for the changes in vegetation were examined. This study was conducted on the Jornada Experimental Range, which is 23 mi north of Las Cruces, New Mexico.