In 1752 Dinwiddie was cut from the westernmost part of Prince George County.
No grants were made in that part of Charles City that became Dinwiddie until 1638. The first patent was to Nathaniel Tatum for land near the falls of the James, not far from Petersburg. The Indian attacks of 1644 were directly responsible for the settlement of the area that became Dinwiddie. In order to provide greater protection the General Assembly in 1645 established a chain of forts at the fall line of the rivers - Fort Charles at present day Richmond, Fort Royal at Pamunkey, Fort James at the ridge of the Chickahominy, and Fort Henry at the falls of the Appomattox.
Fort Henry encompassed Basses Choice and was a part of Prince George County in 1702 when that county was cut from Charles City. The western portion of Prince George County grew over time causing the creation of additional parishes. Until 1720 Bristol served the southern part of Henrico, the present Dinwiddie, and the western part of present Prince George. When Brunswick was split off from Prince George, a slice was cut from Bristol and a new parish constituted for Brunswick County. In 1742, Bath Parish was created from the western part of Bristol. The area that became Dinwiddie lay chiefly in Bath Parish, the eastern portion of the county retained by Bristol. The parishes were divided by a line beginning at the Appamottox River, on the east side of Wallce Creek, and thence a south course to the Surry County line. The early churches of Bath Parish were Sapony and Hatcher's Run, both established in Bristol Parish before the creation of Bath, and later Butterwood.
Source: The Countrey of the Apamatica, WPA, http://www.vagenweb.org/dinwiddie/apamatica/ch1.htm
Modern day adjacent counties are: Nottoway County, Amelia County, Chesterfield County, Petersburg County, Prince George County, Greensville County, Sussex County, and Brunswick County.