Carlyle quickly met with financial success and, in 1747, married Sarah Fairfax, cousin of Thomas Fairfax, 6th Lord Fairfax of Cameron, from one of the most influential families in Virginia. From 1751–53, he built his house, now Carlyle House, in Alexandria and he also owned thousands of acres of land throughout Virginia, including three plantations. His business ventures included trading with England and the West Indies, retail operations in Alexandria, a foundry in the Shenandoah Valley, milling, and operation of a forge. He also undertook a number of civic and religious positions typical of a man of his status.

Carlyle and his wife, Sarah Fairfax, moved into the house on 1 August 1753, the day Sarah gave birth to Carlyle's first son, William.

In 1755, the house was the initial headquarters for Major-General Edward Braddock in the Colony of Virginia during the French and Indian War. The Congress of Alexandria convened in the dining room of the house and here Braddock decided to make an expedition to Fort Duquesne which would result in his death. He was urged not to undertake the expedition by native Virginian George Washington who was then a volunteer aide-de-camp to Braddock. Braddock first suggested the idea of levying additional new taxes on the colonists to help with the cost of the war at the house.

http://www.pbs.org/wgbh/pages/frontline/shows/secret/famous/washington.html

George Washington is connected to this particular family of mixed race Bahamian heritage (read the story of the Fairfaxes and George Washington). Suspicions are that Anne Fairfax, Mount Vernon's first mistress and the wife of Lawrence Washington, the President's brother, was a woman of colour whose mother was born in the Bahamas. A number of George Washington's historians have pointed out that when Anne's brother, George William, visited his Fairfax aunts in England, he had been utterly humiliated by their curiosity over whether he would turn black at puberty. Since the Fairfaxes were a wealthy, titled English family whose members corresponded regularly with each other, there must have been some foundation for this assumption regarding George William's race. Indeed, from one of his father's letters I came across, I discovered that his Fairfax relatives, in point of fact, actually knew his mother, Sarah Walker, the daughter of the Chief Justice of the Bahamas, since she had resided with them in England while on a visit from the West Indies. It is all too obvious then that there must have been a substantial proportion of her ethnic heritage evident, if her in laws expected George William to inherit these African traits as well.

Besides their relationship to Mount Vernon, another historical point about this family is that because of their enormous wealth and their social position in the British Colonial government of the time, William, Sarah's husband, was the first person for whom George Washington ever worked. George William, their son, would, for the rest of his life, be counted as the president's closest friend.

Laurence Washington, like his brother George, did not father any children. However, Ann Fairfax's second marriage was to one of the Lees. With George Lee, Anne finally succeeded in leaving a line even if not a political or culturally dynamic one. From her sister, Sarah's marriage to Major John Carlyle, however, are descended some of the most politically influential families of the South.