This report develops the theory of a cropland use model, reports the results of estimating land devoted to crop production, and shows example applications of the cropland use model in estimating planted acreage response for corn, sorghum, barley, oats, soybeans, and wheat. The model first estimates the total amount of land that will be planted to principal crops and then allocates cropland planted to specific crops. The research is aimed at improving modeling work for major field crops.