Peter Van Dorn graduated from Princeton in 1795 with courses in theology and law. He married and moved to Virginia, where his wife died. At the age of 21 he moved to the Territory of Mississipi, first at Natchez. In 1804 he was appointed Marshal of Natchez by Governor Claiborne. He was a lawyer and became judge of the Probate Court, and at some point settled in Port Gibson. He was also clerk of the Circuit Court, and would ride circuit from Port Gibson to Natchez, forty miles away.
In 1817, the year of statehood,Peter Van Dorn became the first Clerk of the Miss. House of Representatives. Four years later the Legislature selected him to work with Dr. Wm. Lattimore and Gen. Thomas Hinds to design the new capital city of Jackson. Peter Van Dorn created the layout for Jackson, containing parks or green systems interspersed with areas for public buildings, followin a checkerboard plan suggested by Thomas Jefferson.
Peter Van Dorns second wife, Sophia Donelson Caffery, was of a prominent Tennessee family. She was the grandaughter of Col. John Donelson, said to be of General Washington's staff, who settled the Tennessee frontier around Nashville. Her aunt, Rachel Donelson, was married to President Andrew Jackson. General Jackson would often stop at the Van Dorn's as he traveled from Nashville to Natchez. In 1830 Peter Van Dorn took his daughter Octavia to New York and Washington D.C. and visited President Jackson in the White House.
Peter Van Dorn died Feb 12, 1837 and was buried in Port Gibson's Wintergreen Cemetery. Eventually his son Major General Earl Van Dorn CSA would be laid to rest next to his father Judge Peter Aaron Van Dorn.