Maps & Air Photos: Historical Maps

The online map collections represents only a small fraction that have been converted to digital form of the LOC's map collections numbering over 5.5 million maps, 80,000 atlases, 6,000 reference works, over 500 globes and globe gores, 3,000 raised relief models, and a large number of cartographic materials in other formats, including over 19,000 cds/dvds.

Only a small number of maps are available for 1880 and 1890, but the number of maps increases with each succeeding census. An enumeration district was an area that could be covered by a single enumerator or census taker in one census period that lasted several weeks. Enumeration districts varied in size from several city blocks in densely populated urban areas to a large part of a county in sparsely populated rural areas. Boundaries changed from census to census, and these maps show the precise enumeration district or census tract boundaries and numbers used for each census. Beginning in 1910, the maps were drawn in such a way that the enumeration district boundaries coincided with other legal boundaries. The map content varies greatly between states and over time. Early base maps include postal route maps, General Land Office maps, soil survey maps, and maps produced by city, county, and state government offices as well as commercial printers. These base maps were then annotated by census officials to show enumeration district boundaries and numbers that would be used in a specific census year. In addition to enumeration district or census tract boundaries and numbers, some of these maps show wards, precincts, incorporated areas, urban unincorporated areas, townships, census supervisors' districts, split enumeration districts, congressional districts, and other features.

The census tract and standardized maps began to appear with the 1970 census, and later census maps are standardized in appearance, content, and size. More recent maps in this series include metropolitan maps, urbanized area maps, standard metropolitan statistical area maps, census block maps, census tract outline maps, and county block maps. Also included in this series are detailed maps of areas selected for special censuses, 1964-1969 and listings of comparable 1960 and 1970 census tract and block numbers for selected cities.