Bus to Washington, D.C. formally the District of Columbia and commonly referred to as Washington, the District, or simply D.C., is the capital of the United States, founded on July 16, 1790. The City of Washington was originally a separate municipality within the Territory of Columbia until an act of Congress in 1871 effectively merged the City and the Territory into a single entity called the District of Columbia. It is for this reason that the city, while legally named the District of Columbia, is known as Washington, D.C. The city is located on the north bank of the Potomac River and is bordered by the states of Virginia to the southwest and Maryland to the other sides. The District has a resident population of 591,833; however, because of commuters from the surrounding suburbs, its population rises to over one million during the workweek. The Washington Metropolitan Area, of which the District is a part, has a population of 5.3 million, the ninth-largest metropolitan area in the country.
Article One of the United States Constitution provides for a federal district, distinct from the states, to serve as the permanent national capital. The centers of all three branches of the federal government of the United States are located in the District, as are many of the nation's monuments and museums. Washington, D.C., hosts 174 foreign embassies as well as the headquarters of the World Bank, the International Monetary Fund (IMF), the Organization of American States (OAS), the Inter-American Development Bank, and the Pan American Health Organization (PAHO). The headquarters of other institutions such as trade unions, lobbying groups, and professional associations are also located in the District.
The United States Congress has supreme authority over Washington, D.C.; residents of the city therefore have less self-governance than residents of the states. The District has a non-voting at-large Congressional delegate, but no senators. D.C. residents could not vote in presidential elections until the ratification of the Twenty-third Amendment to the United States Constitution in 1961.
Washington, D.C. is a planned city. The design for the City of Washington was largely the work of Pierre (Peter) Charles L’Enfant, a French-born architect, engineer, and city planner who first arrived in the colonies as a military engineer with Major General Lafayette during the American Revolutionary War. In 1791, President Washington commissioned L'Enfant to plan the layout of the new capital city. L'Enfant's plan was modeled in the Baroque style, which incorporated broad avenues radiating out from rectangles and circles, providing for open space and landscaping. In March 1792, President Washington dismissed L'Enfant due to his insistence on micromanaging the city's planning, which had resulted in conflicts with the three commissioners appointed by Washington to supervise the capital's construction. Andrew Ellicott, who had worked with L'Enfant surveying the city, was then commissioned to complete the plans. Though Ellicott made revisions to the original plans, including changes to some street patterns, L'Enfant is still credited with the overall design of the city.The City of Washington was bounded by what is now Florida Avenue to the north, Rock Creek to the west, and the Anacostia River to the east.
By the start of the 20th century, L'Enfant's vision of a capital with open parks and grand national monuments had become marred by slums and randomly placed buildings, including a railroad station on the National Mall. In 1900, Congress formed a joint committee, headed by Senator James McMillan, charged with beautifying Washington's ceremonial core. What became known as the McMillan Plan was finalized in 1901. It included the re-landscaping of the Capitol grounds and the Mall, constructing new Federal buildings and monuments, clearing slums, and establishing a new citywide park system. Architects recruited by the committee kept the city's original layout, and their work is thought to be the grand completion of L'Enfant's intended design.

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Washington, D.C. is divided into four quadrants. After the construction of the twelve-story Cairo Apartment Building in 1899, Congress passed the Heights of Buildings Act, which declared that no building could be taller than the Capitol. The Act was amended in 1910 to restrict building height to the width of the adjacent street plus 20 feet (6.1 m). Today the skyline remains low and sprawling, in keeping with Thomas Jefferson's wishes to make Washington an "American Paris" with "low and convenient" buildings on "light and airy" streets. As a result, the Washington Monument remains the District's tallest structure. However, Washington's height restriction has been assailed as a primary reason why the city has limited affordable housing and traffic problems as a result of urban sprawl. To escape the District's height restriction, taller buildings close to downtown are often constructed across the Potomac River in Rosslyn, Virginia.
The District is divided into four quadrants of unequal area: Northwest (NW), Northeast (NE), Southeast (SE), and Southwest (SW). The axes bounding the quadrants radiate from the U.S. Capitol building.All road names include the quadrant abbreviation to indicate their location. In most of the city, the streets are set out in a grid pattern with east–west streets named with letters (e.g., C Street SW) and north–south streets with numbers (e.g., 4th Street NW). The avenues radiating from the traffic circles are primarily named after states; all 50 states are represented, as well as Puerto Rico and the District itself. Some Washington streets are particularly noteworthy, such as Pennsylvania Avenue, which connects the White House with the U.S. Capitol, and K Street, which houses the offices of many lobbying groups. Washington hosts 174 foreign embassies, 59 of which are located on a section of Massachusetts Avenue informally known as Embassy Row.

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