What is Arlington County, Virginia?
{{Infobox U.S. county | county = Arlington County | state = Virginia | type = [[County (United States)|County]] and [[census-designated place]] | official_name = | flag = Flag of Arlington County, Virginia.svg | logo = Logo of Arlington County, Virginia.png | seal = | founded = February 27, 1801 | area_total_sq_mi = 26 | area_land_sq_mi = 26 | area_water_sq_mi = 0.2 | area percentage = 0.4 | population_as_of = 2020 | population_total = 238643 | population_density_sq_mi = auto | web = http://www.arlingtonva.us/ | ex image = Rosslyn, Arlington, Virginia.jpg| | ex image size = 300px | ex image cap = Arlington's Rosslyn neighborhood seen across the [[Potomac River]] from [[Washington Harbour]] | district = 8th | time zone = Eastern | named for = [[Arlington House, The Robert E. Lee Memorial|Arlington House]] | coordinates = {{coord|38.880278|-77.108333|type:city_region:|display=inline,title}} }} [[File:ArlingtonCLM.JPG|227x227px|thumb|Arlington National Cemetery|right]] [[File:1878 Alexandria County Virginia.jpg|thumb|right|250px|1878 map of Alexandria County, now Arlington County]] [[File:ArlingtonTODimage3.jpg|thumb|right|320px| Aerial view of a growth pattern in Arlington County, Virginia. High density, mixed use development is often concentrated within 1/4 to 1/2 mile from the county's Metrorail [[rapid transit]] stations, such as in [[Rosslyn, Virginia|Rosslyn]], [[Courthouse, Virginia|Courthouse]], and [[Clarendon, Virginia|Clarendon]] (shown in red from upper left to lower right).]] '''Arlington County''' is a county in [[Virginia]]. It has so many buildings that it looks like a city. It is one of the smallest counties in the United States by area. It is across the [[Potomac River]] from [[Washington, D.C.]], and parts of it were once part of Washington. In 2020,