Cabell was born on March 13, 1730, near Licking Hole Creek in what was then vast
Goochland County, Virginia. The firstborn son of physician, planter and surveyor
William Cabell (1699–1774), who had emigrated from
Warminister, England, and his wife the former Elizabeth Burks (1705–1756), he would have younger brothers
Joseph Cabell (1730–1798),
John Cabell (1735–1815) and
Nicholas Cabell (1750–1803), and a sister Mary. All the Cabell brothers (and Mary's husband
John Horsley) became patriots in the American Revolutionary War shortly after their father's death, and married well (thus making their family one of the
First Families of Virginia), as they operated plantations using enslaved labor, and served in the
Virginia General Assembly and local governments. Cabell's father returned to England for several years to settle his father's estate, during which time he often wrote his wife about the boy's education. Elizabeth Burks Cabell ran her family's estates and greatly increased them during this time (including by buying slaves). According to family tradition, after receiving a private education suitable to his class from his parents and tutors at home, this William Cabell studied at the
College of William and Mary in
Williamsburg. At some point the college acknowledged his qualifications as surveyor, so by 1749, he was assisting in his father's surveying business. His public career would begin in 1751 as he joined his father as a
vestryman of
St. Anne's Parish in
Albemarle County, Virginia. Two years later he received an official appointment as
surveyor in his own right. As settlement proceeded westward through Virginia's Piedmont, the Virginia General Assembly created Albemarle County from the western section of Goochland County in 1744, and would create
Buckingham County from the southern part of Albemarle County and
Amherst County from the western section in 1761. Joseph and John Cabell would represent Buckingham County for many terms and Nicholas Cabell (who inherited his father's last plantation, called "Liberty Hall") would represent Amherst County during many legislative sessions (although "Liberty Hall's address would become Nelson County when it was created from Amherst County). This William Cabell married Margaret Jordan, daughter of future one-term Buckingham County Burgess Col.
Samuel Jordan in 1756. Seven children survived their father. Their firstborn,
Samuel Jordan Cabell, was born the year of their marriage and would like his father become a planter and politician, serving in the U.S. Congress as well as Virginia House of Delegates. His slightly younger brother Margaret Cabell bore
William Cabell, Jr. (1759–1822), who also served in the Continental Army, married the daughter of Virginia judge
Paul Carrington and succeeded his father at "Union Hill," most of which became part of
Nelson County during that county's creation from parts of both Albemarle and Amherst counties in 1808. Their two other sons were Landon Cabell (1765–1834) and Hector Cabell (1768–1807), with Hector's widow marrying judge William Daniel and helping raise future justice
William Daniel. Their three daughters all married well. Margaret married prominent Nelson County planter and merchant Robert Rives; their son
William Cabell Rives would have a distinguished legal and diplomatic career. Paulina (1763–1845) married Maj. Edmund Read and after his death c. 1808 Rev. Nash LeGrand. Their youngest daughter Elizabeth (1774–1801) married her cousin
William H. Cabell (1772–1853; Nicholas' son), who became governor of Virginia and, after her death, president of what later became the
Virginia Supreme Court. ==Colonial planter, politician and military officer==