Alexandria is an independent city in the northern region of the Commonwealth of Virginia, United States. It lies on the western bank of the Potomac River approximately 7 miles (11 km) south of downtown Washington, D.C. Alexandria is the third largest "principal city" of the Washington metropolitan area which is part of the larger Washington-Baltimore combined statistical area. As of the 2020 U.S. census, its population of 159,467 made it the sixth-most populous city in Virginia and the 169th-most populous city in the nation. The city's estimated population has grown by 1% annually since 2010 on average. Like the rest of Northern Virginia and Central Maryland, modern Alexandria has been influenced by its proximity to the U.S. capital. It is largely populated by professionals working in the federal civil service, in the U.S. military, or for one of the many private companies which contract to provide services to the federal government. One of Alexandria's largest employers is the U.S. Department of Defense. Another is the Institute for Defense Analyses. In 2005, the United States Patent and Trademark Office moved to Alexandria, and in 2017, so did the headquarters of the National Science Foundation. The historic center of Alexandria is known as Old Town Alexandria, or simply "Old Town". With its concentration of boutiques, restaurants, antique shops and theaters, it is a major draw for all who live in Alexandria as well as for visitors. Like Old Town, many Alexandria neighborhoods are compact and walkable. It is the 6th largest and highest-income independent city in Virginia. A large portion of adjacent Fairfax County, mostly south but also west of the city, has Alexandria mailing addresses. However, this area is under the jurisdiction of Fairfax County's government and separate from the independent city. The city is therefore sometimes referred to as the "City of Alexandria" to avoid confusion. Neighboring Arlington County was formerly named "Alexandria County" before it was renamed by the Virginia General Assembly in 1920 to reduce confusion with the city.