According to ESRI's Guide to Geographic Information Systems (GIS), GIS is a collection of computer hardware, software, and geographic data for capturing, managing, analyzing, and displaying all forms of geographically referenced information. Historical GIS (HGIS) is an emerging field that uses GIS to research the geographies of the past. Regarded as a subfield of historical geography, HGIS displays, stores, and analyzes data of past geographies and tracks changes over time. This has resulted in digital archives of interest to researchers. The University of Portsmouth (UK) created and maintains the Great Britain Historical Geographical Information System. This digital collection shows the changes over time within British regions -- its information sources include census reports (1801-2001), historical gazetteers, travelers' stories, and historic maps. Meanwhile, there are already some Web resources and services for GIS and HGIS. One site devoted to HGIS, historical cartography, and historical geography is his-GIS.net.