According to jibin123, Washington, D.C. is the capital of the United States, and is located in the District of Columbia. Together they form one entity. Surrounding it are the suburbs of Virginia and Maryland. Washington itself has 670,000 inhabitants (2021), with an urban area of 6,356,000 inhabitants (2021).
Introduction
The conurbation is located on both banks of the Potomac River. The agglomeration is heavily forested, stretching 55 kilometers from east to west, and 60 kilometers from north to south. The city is about 180 kilometers from the coast, although the various inlets of the Chesapeake Bay reach all the way to the city. The lowest point is therefore sea level. The urban area does not go much higher than 140 meters. The largest suburbs are Arlington and Alexandria, surrounded by numerous smaller suburbs in the woods in Virginia. The urban area is therefore not densely built-up. So are the Maryland suburbs, the largest of which have barely more than 50,000 residents. Housing in Maryland is cheaper than in Virginia.
The Washington metropolitan area has actually grown close to Baltimore, which lies to the northeast. Baltimore, in turn, has become attached to Philadelphia, which in turn is attached to New York, and that in turn to the Connecticut and Massachusetts metropolitan area near Boston. Together, these agglomerations form the so-called Boswash area, the urban area on the east coast from Boston to Washington. Furthermore, Washington is not far from Maryland’s capital, Annapolis.
The climate is humid and subtropical. In winter it can get quite cold with snow. Hurricanes remnants can bring heavy rainfall, and high tides can push the Potomac River to such an extent that flooding is possible. Washington is a city associated with bureaucracy, as the federal government sits here, and many other organizations. This causes a lot of commuting between the suburbs and Washington.
Population growth
The metropolitan area is centered around the District of Columbia, which corresponds to the city of Washington. In Maryland, two counties are suburban, in Virginia there are three counties and 6 independent cities as part of the suburban area. The independent cities are included in the overview below for the relevant counties. In addition, there are a number of exurban counties that are not included in the overview.
| Year | Washington DC | Montgomery, MD | Prince George’s, MD | Fairfax, VA | Prince William, VA | Loudoun, VA | total |
| 1920 | 438,000 | 35,000 | 43,000 | 56,000 | 14,000 | 21,000 | 607,000 |
| 1930 | 487,000 | 49,000 | 60,000 | 78,000 | 14,000 | 20,000 | 708,000 |
| 1940 | 663,000 | 84,000 | 89,000 | 135,000 | 18,000 | 20,000 | 1.009.000 |
| 1950 | 802,000 | 164,000 | 194,000 | 304,000 | 23,000 | 21,000 | 1,508,000 |
| 1960 | 764,000 | 341,000 | 357,000 | 539,000 | 50,000 | 25,000 | 2,076,000 |
| 1970 | 757,000 | 523,000 | 661,000 | 773,000 | 111,000 | 37,000 | 2,862,000 |
| 1980 | 638,000 | 579.000 | 665,000 | 883,000 | 145,000 | 57,000 | 2,967,000 |
| 1990 | 607,000 | 757,000 | 729.000 | 1,131,000 | 216,000 | 86,000 | 3,526,000 |
| 2000 | 572,000 | 873,000 | 801,000 | 1,319,000 | 326,000 | 170,000 | 4,061,000 |
| 2010 | 602,000 | 972,000 | 863,000 | 1,430,000 | 440,000 | 312,000 | 4,619,000 |
| 2020 | 690,000 | 1,061,000 | 966,000 | 1,585,000 | 483,000 | 423,000 | 5,208,000 |
| 2021 | 670,000 | 1,055,000 | 955,000 | 1,566,000 | 484,000 | 428,000 | 5,158,000 |
The city of Washington was without a suburban area before the 1920s, which only started to grow in the 1950s. In 1950 the city also had its highest population, after which a long, but slow decline set in. At the same time, the suburban area began to grow strongly. Growth has slowed somewhat in Maryland since the 1990s, but is still strong, especially in Virginia.
Road network
The highways around Washington DC
The city is served by the Capital Beltway ring road, the I-495. Coming from the south, I-95 rides on the ring road, then continues toward Baltimore and New York. From the west comes I-66, connecting northern Virginia to the city. Other main Interstate routes do not serve the city, I-70 continues north to Baltimore, and I-97 connects Annapolis to Baltimore east of the city. There are, however, plenty of auxiliary routes, such as I-295 and I-395, which serve the southern suburbs, and I-270, which runs northwest, connecting to Pittsburgh. The US 50 also complements this network, connecting Washington with Annapolis.
In addition, there are numerous State Routes and Parkways that complement the network at the local level. The ring road has 2×4 lanes everywhere, but a few incoming highways have a number of bottlenecks with 2×2 lanes. In view of the population, the motorway network is quite undersized. Many highways converge around the Pentagon, creating a complex web of interchanges. There are some toll roads or toll lanes around the agglomeration. Some highways also have HOV lanes.
Washington’s local road network is a grid model, and unlike many other grid-based cities, there are also many diagonal roads that converge at the Capitol. The secondary road network outside of Washington itself is non-grid, with a number of major thoroughfares, and further winding residential streets, so that a lot of traffic takes the highway.
List of freeways
| name | length | first opening | last opening | max AADT 2012 |
| Custis Memorial Parkway | 58 km | 1961 | 1982 | 177,000 |
| Shirley Memorial Highway | 42 km | 1952 | 1965 | 201,000 |
| Interstate 270 | 29 km | 1955 | 1960 | 252,000 |
| Anacostia Freeway | 13 km | 1964 | 1964 | 87,000 |
| Interstate 370 | 5 km | 199x | 199x | 90,000 |
| Shirley Memorial Highway | 16 km | 1941 | 1952 | 213,000 |
| Washington Beltway (Virginia) | 37 km | 1961 | 1964 | 236,000 |
| Washington Beltway (Maryland) | 66 km | 1957 | 1964 | 227,000 |
| John Hanson Freeway | 20 km | 1957 | 1957 | 146,000 |
| Pennsylvania Avenue | 16 km | 1970 | 1970 | 70,000 |
| Branch Avenue | 8 km | 1999 | 2001 | 123,000 |
| Harry Byrd Highway / Leesburg Bypass | 17 km | ? | 2021 | 59,000 |
| Washington Boulevard | 4 km | 1941 | 1941 | 105,000 |
| Sully Road | 21 km | 1988 | 2011 | 133,000 |
| Jefferson Davis Highway | 4 km | 1941 | 1941 | 79,000 |
| Intercounty Connector | 30 km | 2011 | 2011 | 35,000 |
| Dulles Toll Road | 46 km | 1962 | 1995 | 132,000 |
| Washington-Baltimore Parkway | 24 km | 1954 | 1954 | 105,000 |
| Clara Barton Parkway | 8 km | 1964 | 1973 | ? |
| George Washington Memorial Parkway | 22 km | 1932 | 1932 | ? |
| Suitland Parkway | 15 km | 1944 | 1944 | ? |
History
Washington, DC is a planned city, the road network being designed in the L’Enfant Plan of 1791, developed by Pierre Charles L’Enfant (1754-1825) for President George Washington. In the plan, a grid was developed, with literate roads that would run east-west and numbered roads that would run north-south. Diagonal routes were conceived as grand avenues, named after the states of the time. These large avenues intersected the major north-south and east-west roads through ‘circles’ or square intersections.
Unlike New York City, a highway network in Washington DC didn’t get off the ground as early as the 1930s, despite it being quite a large city back then. The oldest plans date back to the 1940s. The George Washington Memorial Parkway that crosses the bank of the Potomac River in Virginia is one of the oldest highway-like roads, opening to traffic about 1932. In 1941, a highway network was built around the then newly built Pentagon, which is home to the US Department of Defense. This “Pentagon Road Network” included portions of what is now State Route 27, State Route 110, and Interstate 395 in Arlington. It was not until the 1960s that these highways were handed over to the state of Virginia. In the 1940s, plans were further made for a number of highways, namely the Baltimore-Washington Parkway, the Washington National Pike and the Shirley Highway. The Baltimore-Washington Parkway began construction in 1947, the first section of which opened to traffic in 1950. In 1954, the highway between Washington DC and Baltimore was completed. The Shirley Highway was also constructed between 1945 and 1952, a highway-like road from Arlington to Woodbridge in Virginia, which would later become part of I-395 and part of I-95 south of Washington DC. The third plan was the Washington National Pike, which was later designated I-270. It runs northwest from Bethesda to Frederick and was opened between 1951 and 1960. These three highways predate the Interstate Highway system. In 1957, the John Hanson Highway, a highway from Washington DC to Maryland’s capital Annapolis, opened. This one actually predates the Interstate Highway system as well. Washington DC was thus connected in 4 directions by highway by the late 1950s.
Beginning in 1960, more highways around Washington DC were completed. Chief among these was Interstate 495, better known as the Capital Beltway, the city’s beltway. It opened to traffic in stages between 1961 and 1964. Originally, it was planned to have Interstate 95 go right through Washington DC, as is common in other American cities. As early as the 1960s, it was anticipated that urban traffic would increase sharply, and that plug-ins from the Beltway to Washington DC were necessary. One plan of these was I-270 from Betshesda to the then-planned I-95 through Washington. Both plans fell through in the 1970s. In 1977, I-95 was rerouted outside Washington DC, over the eastern portion of the Capital Beltway. In 1971, the I-95 between Washington and Baltimore was completed, that relieved the old Baltimore-Washington Parkway. One of the biggest bottlenecks to build was Interstate 66 through Arlington. It had been planned since the 1950s, but was finally opened in 1982. It is the only Interstate Highway where HOV restrictions are in effect for the entire highway during rush hour. Trucks and vehicles with less than 2 people are not allowed to drive on the highway. By the 1980s, traffic around Washington DC had increased dramatically due to rapid suburbanization in Virginia and Maryland. The city was known as one of the worst bottlenecks in the United States. Most highways were widened in the 1980s, such as I-95, I-270 and I-495. Later, more highways were widened, most prominently I-395 with a reversible lane, I-95 south of Washington with switch, HOV and HOT lanes, and the widening of the Woodrow Wilson bridge from 6 to 12 lanes. Already in the 1970s it was foreseen that with the guiding of I-95 over the eastern ring road, it would no longer suffice, and a second ring road around Washington was necessary. However, this was never built, although the Intercounty Connector (SR-200) opened in Maryland in 2011 is a possible start. There have been plans for a second ring road, but most of these would run too far outside Washington to be of use to through traffic.
Congestion
Washington has always had a lot of congestion on the Southern Beltway, because the bridge over the Potomac had only 2×3 lanes. Now 12 lanes are available there, and the Springfield interchange has also been adapted, so that the traffic jams here are a thing of the past. There are quite a lot of bottlenecks on other incoming highways, and long traffic jams often occur here. Travel time in Washington is quite high for commuters nationally, with more than 20% having a travel time of more than an hour. Only 20% have a journey time of less than 20 minutes, the highest number in the country.
