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In addition, NHGIS has created historical and contemporary cartographic boundary shapefiles compatible with every census, and over 50 million lines of metadata describing the collection. Historical U.S. state and county boundaries are available 1790–present, with smaller geographies available as the U.S. Census Bureau created them.
NHGIS provides free of charge, aggregate census data and GIS-compatible boundary files for the United States between 1790 and 2012. Atlas of Historical County Boundaries Project (AHCBP) The AHCBP documents all boundary changes in states and counties in United States territory, including non-county areas never before compiled or mapped ...
The data was entered in spreadsheet format or in ESRI shapefiles and submitted via e-mail to the USGS National Geospatial Technical Operations Center(s) in Denver, Colorado, and Rolla, Missouri. During the registration process, prospective volunteers submitted a list of the 7.5 minute quadrangle maps on which they wished to work.
In 2008, data in shapefile format was published. Please note that shapefiles are not topological, therefore may create slivers when comparing TIGER/Line boundaries. This mismatch was not possible when the census TIGER files were available in ASCII format that was topological unlike shapefiles.
The shapefile format is a geospatial vector data format for geographic information system (GIS) software.It is developed and regulated by Esri as a mostly open specification for data interoperability among Esri and other GIS software products. [1]
Shapefiles : are a data exchange format created by ESRI and one of the most widely used GIS/geodata formats. One "shapefile" usually include four different files : .shp, .shx, .dbf, .prj. First three files must all be present in order to use the data. Each shapefile can hold only one geometry type.
[2] Although it is a public database, GADM has a higher spatial resolution than other free databases, [3] and also higher than commercial software such as ArcGIS. [4] Those sources are commonly use to complete data analysis with data visualisation such as data plots , choropleth map , etc. [ 5 ] [ 6 ]
Date/Time Thumbnail Dimensions User Comment; current: 01:19, 16 February 2008: 4,000 × 2,671 (62 KB): Brianski == Summary == {{Information |Description=Map of states of the USA in actual positions, Lambert Conic projection |Source=Derived from usa2000.shp |Date=2008/02/15 |Author=Brian Szymanski |Permission=see below }}