The CARD-RCA linear programming model of United States agriculture has evolved through more than a decade of detailed research at the Center for Agricultural and Rural Development. At the present time, the model is equipped for endogenous treatment of the production and transportation of the major crops in U.S. agriculture. An optional livestock sector is also available. The model has been used for analysis of several topics of interest to policy makers, academics, and producers in the private sector. Under contract with the Soil Conservation Service, the model is being further developed in preparation for more extensive use by the government, and several potential avenues to improvement are being explored. This paper explains the need for including rangeland and permanent pasture use as an endogenous sector in the CARD-RCA model. Also, the problems of modeling rangeland use are discussed, and a methodology for constructing the range sector is examined. This report, therefore, is preliminary in nature and intended for use of CARD, SCS, and FS personnel as they review the needs for the research project at hand. Actual documentation of the grazing sector will be prepared once the sector has been constructed and tested for use in the CARD-RCA models.