Welcome to Arlington!

Arlington County is an urban county of about 203,000 residents in the Commonwealth of Virginia, in the U.S., directly across the Potomac River from Washington, D.C. [1] Originally part of the District of Columbia, the land now comprising the county was retroceded to Virginia in a July 9, 1846 act of Congress that took effect in 1847. At a land area of 26 square miles, it is the geographically 4th smallest self governing county in the United States. Arlington was ranked as the most educated city (percentage of residents with graduate degrees) in 2006 by CNN Money. It is the location of Arlington National Cemetery and the Pentagon.

Once part of Fairfax County in the Virginia Colony, the area that contains Arlington County was ceded to the U.S. government by the Commonwealth of Virginia to a surveying team that Andrew Ellicott led placed them in their present locations.
In 1791, the U.S. Congress established the final limits of the federal territory that would house the nation's capital as a square with 10 miles on each side, the maximum area permitted by Article I, Section 8, of the United States Constitution. However, the legislation that established these limits contained a provision that prevented the U.S. government from locating any federal offices within the portion of the territory that Virginia had ceded.
When Congress moved to the new District of Columbia in 1801, it enacted legislation that divided the District into two counties: (1) the county of Washington, which lay on the east side of the Potomac River, and (2) the county of Alexandria, which lay on the west side of the River. Alexandria County contained at the time a rural area that included the present Arlington County, as well as the urbanized town of Alexandria (now "Old Town" Alexandria), a port that was located on the Potomac River in the southeastern part of the present City of Alexandria.
Although some residents of Alexandria County had earlier hoped, for better or for worse, to benefit from the land sales and increased business activity that the federal capital's location might inspire, this benefit failed to appear. Instead, political and economic competition grew with the town of Georgetown, a port that was located in Washington County adjacent to the capital city (Washington City).
As the U.S. government could not establish any federal offices in the County, and as the economically important Chesapeake and Ohio Canal (C&O Canal) on the north side of the Potomac River favored Georgetown, Alexandria's economy stagnated. This stagnation worsened as some of Georgetown's residents opposed federal efforts to maintain the Alexandria Canal, which connected the C&O Canal in Georgetown to Alexandria's port. Further, as they were residents of the District of Columbia, Alexandria's citizens had no representation in Congress and could not vote in federal elections.
In addition, Alexandria had become a port and market for the slave trade. As there was increasing talk of abolishing slavery in the nation's capital, some Alexandrians feared that the local economy would suffer if the federal government abolished slavery in the District of Columbia.
Simultaneously, there arose in Virginia an active abolitionist movement that created a division on the question of slavery in Virginia's General Assembly (Later, during the Civil War, Virginia's division on the slavery issue contributed to the formation of the state of West Virginia by its most anti-slavery counties). Pro-slavery Virginians recognized that Alexandria County could provide two new representatives who favored slavery in the General Assembly if the County joined the Commonwealth.
As a result, a movement grew to separate Alexandria County from the District of Columbia. After a referendum, the county's residents petitioned the U.S. Congress and the Virginia legislature to permit the County to return to Virginia. The area was retroceded to Virginia on July 9, 1846.
In 1852, the independent City of Alexandria was incorporated from a portion of Alexandria County. This created an ambiguity, as two separate legal entities had similar names. Alexandria County eventually renamed itself in 1920 to Arlington County. The county's new name derived from that of Arlington National Cemetery, whose own name had derived from that of Confederate General Robert E. Lee's former home, Arlington House, which since the Civil War had been located within the cemetery.