This report is the initial phase of a study to develop, adapt, and integrate models for evaluating the economic effects of expanded coal mining and conversion in the Northern Great Plains (Fort Union) Region. Work under Phase I was designed to determine the usefulness for describing interindustry relationships in western North Dakota, southeastern Montana, and northeastern Wyoming of input-output coefficients previously developed for North Dakota. The 17 sector model (which includes coefficients collected in Phase I for the coal mining, coal fired thermal electric generating, petroleum and natural gas extraction, and petroleum refining sectors) provides personal income estimates that coincide more closely with Department of Commerce estimates than do those obtained with the earlier 13 sector model. It appears that the input-output model can be used for estimating the potential effects of coal resource development in North Dakota.