| Abstract
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The data consist of 13 base map themes acquired by the U.S. Geological Survey (USGS) Helena Office to accompany the coal and water resources data published as USGS Open-File Report 90-568. The report is available from the USGS at http://pubs.er.usgs.gov/pubs/ofr/ofr90568, and the coal and water resource layers are available from the State Library at http://mslapps.mt.gov/Geographic_Information/Data/DataList/datalist_Details.aspx?did={7cd46118ff5146acb51edf7ae2f9d34e}.The base map layers were mostly assembled from 1:100,000 scale USGS Digital Line Graph (DLG) files, which were based on hardcopy maps whose publication dates were from 1979 to 1981. The following layers are available:Roads, Hydrography lines, Hydrography polygons, Miscellaneous transportation (pipelines, powerlines, and airports), and Railroads, from 1:100,000 scale DLG files.Counties and Reservations, from 1:24,000 scale DLG files.River Basins (4th-code hydrologic unit sub-basins), digitized for this project from 1:24,000 scale USGS maps.National Forest Districts, digitized for this project from 1:126,720-scale Custer National Forest visitor's map.Geographic Names, generated from latitude-longitude coordinates available from the Geographic Names Information System (GNIS).Land Use, from USGS 1:250,000 scale Geographic Information Analysis and Retrieval (GIRAS) files. These are based on land use maps made in 1970, 1975, and 1976.7.5-minute (1:24,000 scale) quadrangle boundaries, generated from quadrangle corner latitude-longitude coordinates.60x30-minute (1:100,000 scale) quadrangle boundaries, generated from quadrangle corner latitude-longitude coordinates.The layers are all in UTM Zone 13 NAD 27 coordinates. They were provided to the State Library in ESRI coverage format. Many of the layers were divided into small regional sections. The Library converted the data to shapefiles and combined the regional sections into single datasets for each layer.
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