Soil properties and air-mass backward trajectories were integrated into a geographical information systems (GIS) tool to identify geographical regions that were likely to have significant influence on dust concentrations at Class I national parks and wilderness areas in US. The Windblown Dust Index (WDI) was introduced by spatial analysis of wind erosion and land use/land cover data for North America to identify potential area sources of windblown dust. The spatial probability density maps of backward trajectories were utilized to determine the number of trajectory points that passed near a grid cell at speeds higher than a specified threshold value. Analysis of data for the Salt Creek and White Mountain wilderness areas highlighted the significant potential of both local and regional sources of windblown dust at the two sites, with evidence for seasonal variation. These data are useful in evaluating the importance of windblown dust source areas and developing cost-effective targeted studies and/or mitigation strategies. © 2008 Elsevier Ltd.