I seem to get a lot of questions about my hometown, Washington, D.C. I am actually from a town called Chevy Chase, which is in Maryland, the state directly to the north of Washington, D.C. You can see Chevy Chase on the top-left of the picture below:
However, from my parents' house you can walk into Washington D.C. in about five minutes, so I usually just say that I'm from there to stop any confusion.
The city was established in 1791, which was 15 years after America became a country. Before 1791 the capital of America was Philadelphia, Pennsylvania, which is close to Dave's hometown. The government decided to create a new capital (kind of like with Japan and Kyoto/Tokyo) and Maryland and Virginia donated the land to create the city.
People often refer to the city as simply D.C. The 'D.C.' in the name means 'District of Columbia' - Columbia was a popular nickname for America in use at the time.
Students are often surprised to learn that D.C., despite being a very powerful city, is not a very large one. The population is only about 650,000 people, which makes it the 23rd largest city in America. If you include the suburbs in Maryland and Virginia there are about 6 million people, which is the 7th largest metropolitan area in the U.S.
One reason for its small size is that there is a rule that no building can be taller than the street next to it plus 6 meters. Because of this rule, the Washington Monument, at 169 meters, is the tallest building in the city.
You can also see the White House, where the president lives, in the background.
The last thing I'll mention is that very near the Washington Monument there is an area called the Tidal Basin, which is where the thousands of cherry trees that Japan donated to America in 1912 are planted. It is very popular for Washingtonians (people from D.C.) to have a picnic under the trees.
Here is a link to some more pictures of the National Cherry Blossom Festival: