Loudoun 2010 Census Block Groups

More MetadataThis GIS layer contains the geographical boundaries of the 2010 census block groups for Loudoun County, Virginia. The 2010 Census block group boundaries are used for Census Bureau statistical data tabulation purposes, including the 2010 Decennial Census and American Community Surveys.

Census block groups are part of the sub-county census geography hierarchy of tracts, block groups, and blocks. The three census geographies nest to each other, forming a hierarchy of census tract, followed by block groups, and then blocks, with blocks being the smallest. A census block group is a cluster of census blocks within the same census tract that have the same first digit of their four-digit census block numbers within a census tract.

Loudoun County's block groups were delineated by Loudoun County Government during the Census Bureau's Participant Statistical Areas Program for the 2010 Census. The 2010 Census block layer has been modified from the Census Bureau's Tiger line file. Users should be aware that the Census's Tiger line data is devised from a mix of national and local GIS data sets. When the Tiger line data is overlaid with Loudoun County Government's detailed GIS layers it can be determined that the Census Bureau's Tiger line boundaries in some cases are slightly off from the actual location of the physical features, natural features, and governmental units such as town boundaries that they are designated to follow. The 2010 Loudoun census block group layer was generated by Loudoun County so that the block group boundaries would overlay with the features in Loudoun County's GIS data sets that the boundary are designated to follow.