The wind resource assessment group at the National Renewable Energy Laboratory (NREL), in Golden, Colorado, has produced updated wind energy resource maps for the states of North Dakota, South Dakota and Illinois during the last two years. The updated state maps were created by first analyzing data from recently developed meteorological data sets such as Reanalysis, DATSAV2, and wind measurements from tall towers, and then using a computerized mapping Geographic Information System technique developed at NREL to produce the maps. The updated maps have a 1- km resolution compared to the 25- km resolution of the previous state maps produced during the mid 1980s. The updated maps have been validated where possible using data collected specifically for wind energy resource purposes. The comparisons between the older and newer state wind resource maps revealed some similarities in the wind resource distributions but also some significant differences. For example, the Illinois wind resource map produced in the mid 1980s showed the wind resource throughout the entire state to be too low for economic development. However, the newer map shows areas in the central and northern part of the state with sufficient wind resource for economic development. The updated state maps have already stimulated interest and wind energy development in these areas.