Washington, District of Columbia (D.C.) is the urban area that contains the chief offices of the government of the United States. In modern times, the city of Washington, and the District of Columbia are the same area. It is part of no state; the District of Columbia has some of the governmental authority of a state; it votes for President as would a state, but it only elects a nonvoting delegate to Congress.
Originally, the national capital area was created from lands granted, in 1790, by the states of Maryland and Virginia, forming a 10-mile square divided by the Potomac River. In 1847, the government decided it would never be large enough need all the land available, so it ceded the Virginia portion back to its home state. Before the Virginia side reverted, it was known as Alexandria, D.C. Alexandria later split, in Virginia, into the independent city of Alexandria and the county of Arlington; Arlington contains no cities. At one time, the now upscale area of Georgetown was the working port area of the District of Columbia, and had its own local government.
Technically, the D.C.-Virginia border was the center of the Potomac River. When the Pentagon Building was constructed, on the Virginia side, some land was created from dredging the Potomac, and part of the Pentagon is technically in Virginia, not D.C. In practice, the building has its own postal code, and mail will be delivered to it whether the address says Virginia or D.C.
The original central part of the city was an early example of an urban plan, designed by Pierre L'Enfant, whose technical assistant was the surveyor and astronomer, Benjamin Banneker, born free to former slaves. In many respects, the plan, and subsequent additions, is very logical, with some maddening exceptions. First, the city is divided into four quadrants, centered on the United States Capitol, Northwest, Northeast, Southwest, and Southeast. Within quadrants, the north-south roads are numbered streets, and the east-west ones are lettered. The quadrant is important; there are four intersections of 8th and H Streets.
Avenues run diagonally, meeting at various traffic circles (rotaries, roundabouts, etc.). It had been planned that these would serve as artillery bases for the defense of the city against cavalry, expected to gallop down the avenues and into the muzzles of the cannon. Unfortunately, during the War of 1812, the British neglected to follow the traffic rules and avoided the cannon. During some of the larger protests of the 1970s, the small parks at the centers of the circles were convenient points to assemble troops and police.
There are various oddities in the plan, which, depending on one's choice of legend, either are unexplainable or have many explanation. For example, K street follows I street. Explanations range from a clerical error, to a draftsman whose native language did not include the letter "J", to that L'Enfant was said to despise John Jay, first Chief Justice of the Supreme Court.
After a time, it does not really bother a long-term resident to find things like the one-block long East Street, Northwest. Beyond the lettered streets, the east-west streets are named and generally alphabetical; the first group have one-syllable names, followed by two-syllable, and then three. Exceptions tend to be the norm.
With the exception of the Department of Defense, all cabinet-level agencies have their headquarters in Washington proper, although subordinate organizations are scattered through the District as well as the Maryland and Virginia suburbs. The U.S. government as a whole, of course, has major facilities nationwide.
Although the Capitol complex is the center of the quadrants, it is not the physical center of the city. From the West Front of the Capitol extends the grassy National Mall, with both working offices, museums and monuments along it. The far western side of the Mall ends in the Lincoln Memorial, containing a magnificent sculpture, but in many ways best known as the place from which Martin Luther King Jr. gave his "I have a dream" speech during the 1962 civil march; Hollywood leads many to think of it with Forrest Gump at his side. Slightly northeast of the Lincoln Memorial is the Vietnam Veterans Memorial, often called "the Wall". The obelisk of the Washington Monument, which is the tallest building in the city, is to the southeast of the Lincoln Memorial, still on the Mall.
Roughly midway along the mall, across an additional grassy area called the Ellipse, is the White House, which, although a large residence, surprises many as being relatively small compared to the buildings around it.
The modern city
While the federal presence dominates, the metropolitan area is home to a large number of people, many of whom are government workers and contractors but all the aspects of a large city. The part of Virginia that originally was part of D.C. is linked by a series of bridges, and the Arlington-Alexandria area is, in many respects, an extension of downtown Washington, with residential areas further inland.
Like any large city, it has its own culture; John F. Kennedy, with both government and some earlier urban areas in mind, once called it the city of "Northern charm and Southern efficiency." Nevertheless, there is an active cultural life, from the quasi-public John F. Kennedy Center for the Performing Arts to small jazz clubs; Blues Alley is literally in one.