Substantial county boundary changes are those affecting an estimated population of 200 or more; changes of at least one square mile where an estimated population number was not available, but research indicated that 200 or more people may have been affected; and annexations of unpopulated territory of at least 10 square miles.

The Census Bureau’s reference date for geographic entity boundaries in all geographic and statistical data products is January 1 of the reference year (e.g., January 1, 2019). Boundary changes with effective dates after January 1 will appear in geographic and statistical data products referenced to the following year. For example, a change with an effective date of January 2, 2019 will appear in products referenced to 2020.

Changes are listed below in the decade they occurred.

The Census Bureau does not produce before-and-after maps illustrating the boundary changes. Contact the state or county governments for more specific information about these changes.

1970

Changes to Counties or County Equivalent Entities: 1970s

Changes to County Equivalent Entities in Alaska

The county equivalent entities in Alaska changed from Census Divisions in 1970 to Boroughs and Census Areas in 1980. The inventory and boundaries of the Alaska county-level entities changed substantially during the decade.
New entities created in Alaska are: Dillingham Census Area (02-070), North Slope Borough (02-185), and Valdez-Cordova Census Area (02-261).

Deleted county equivalent entities in Alaska

Angoon Division (02-030)
Barrow Division (02-040)
Cordova-McCarthy Division (02-080)
Kenai-Cook Inlet Division (02-120)
Kuskokwim Division (02-160)
Outer Ketchikan Division (02-190)
Prince of Wales Division (02-200)
Skagway-Yakutat Division (02-230)
Upper Yukon Division (02-250)
Valdez-Chitina-Whittier Division (02-260)

New Counties or County Equivalent Entities

Manassas (independent) city, Virginia (51-683):
Changed from a town to a city and became independent of Prince William County (51-153) effective June 1, 1975; 1970 population: 9,164.
Manassas Park (independent) city, Virginia (51-685):
Changed from a town to a city and became independent of Prince William County (51-153) effective May 1, 1975; 1970 population: 6,844.
Poquoson (independent) city, Virginia (51-735):
Changed from a town to a city and became independent of York County (51-199) effective June 1, 1975; 1970 population: 5,441.

Deleted Counties or County Equivalent Entities

Washabaugh County, South Dakota (46-131):
Combined into Jackson County (46-071) effective January 1, 1979.
Nansemond County, Virginia (51-123):
Combined into Suffolk (independent) city (51-800) effective July 1, 1972.

Substantial County or County Equivalent Entity Boundary Changes

Jackson County, South Dakota (46-071):
Added all of the former Washabaugh County (46-131), effective January 1, 1979.
Bedford County, Virginia (51-019):
Part annexed to Lynchburg (independent) city (51-680), effective December 31, 1975; estimated population: 1,500.
Campbell County, Virginia (51-031):
Part annexed to Lynchburg (independent) city (51-680) effective December 31, 1975; estimated population: 9,000.
Dinwiddie County, Virginia (51-053):
Part annexed to Petersburg (independent) city (51-730) effective December 31, 1971; estimated population: 3,400.
Frederick County, Virginia (51-069):
Part annexed to Winchester (independent) city (51-840) effective December 31, 1970; estimated population: 4,800.
Montgomery County, Virginia (51-121):
Part annexed to Radford (independent) city (51-750) effective December 31, 1976; estimated population: 400.
Prince George County, Virginia (51-149):
Part annexed to Petersburg (independent) city (51-730) effective December 31, 1975; estimated population: 4,700.
Prince William County, Virginia (51-153):
Part taken when Manassas (51-683) and Manassas Park (51-685) became cities and separated from the county effective June 1, 1975, and May 1, 1975, respectively; 1970 population detached: 16,008.
Roanoke County, Virginia (51-161):
Part annexed to Roanoke (independent) city (51-770) effective December 31, 1975; estimated population: 13,500.
Washington County, Virginia (51-191):
Part annexed to Bristol (independent) city (51-520); estimated population: 4,800.
York County, Virginia (51-199):
Part taken when Poquoson (51-735) became a city and separated from the county effective June 1, 1975; 1970 population detached: 5,441.
Bristol (independent) city, Virginia (51-520):
Annexed part of Washington County (51-191); estimated population: 4,800.
Lynchburg (independent) city, Virginia (51-680):
Annexed part of Bedford County (51-019) effective December 31, 1975; estimated population: 1,500. Annexed part of Campbell County (51-031) effective December 31, 1975; estimated population: 9,000.
Petersburg (independent) city, Virginia (51-730):
Annexed part of Dinwiddie County (51-053) effective December 31, 1971; estimated population: 3,400. Annexed part of Prince George County (51-149) effective December 31, 1971; estimated population: 4,700.
Radford (independent) city, Virginia (51-750):
Annexed part of Montgomery County (51-121) effective December 31, 1976; estimated population: 400.
Roanoke (independent) city, Virginia (51-770):
Annexed part of Roanoke County (51-161) effective December 31, 1975; estimated population: 13,500.
Suffolk (independent) city, Virginia (51-800):
Added all of former Nansemond County (51-123) effective July 1, 1972.
Winchester (independent) city, Virginia (51-840):
Annexed part of Frederick County (51-069) effective December 31, 1970; estimated population: 4,800.

Page Last Revised - October 8, 2021

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