On May 2, 1749, the House of Burgesses approved the river location and ordered "Mr.
Washington do go up with a Message to the Council and acquaint them that this House have agreed to the Amendments titled An Act for erecting a Town at Hunting Creek Warehouse, in the County of Fairfax." A "Public Vendue" (auction) was advertised for July, and the county surveyor laid out street lanes and town lots. Almost immediately upon establishment, the town founders called the new town "Belhaven", believed to be in honor of a Scottish patriot, John Hamilton, 2nd Lord Belhaven and Stenton, the Northern Neck tobacco trade being then dominated by Scots.
In 2005, the United States Patent and Trademark Office moved to Alexandria, and in 2017, so did the headquarters of the National Science Foundation.
A large portion of adjacent Fairfax County, mostly south but also west of the city, is named "Alexandria," but it is under the jurisdiction of Fairfax County and separate from the city; the city is sometimes referred to as the City of Alexandria to avoid confusion (see the "Neighborhoods" paragraph below).
One of the sites designated for a warehouse on the upper Potomac River was at the mouth of Hunting Creek.As a result, Philip and his cousin Captain John Alexander (1711–1763) gave land to assist in the development of Alexandria, and are thus listed as the founders.This John was the son of Robert Alexander II (1688–1735).Since the river site was amidst his estate, Philip opposed the idea and strongly favored a site at the head of Hunting Creek (also known as Great Hunting Creek).It has been said that in order to avoid a predicament the petitioners offered to name the new town Alexandria, in honor of Philip's family.