so I guess I am a geography nerd. I was curious the other day to see where the geographic center of DC is, so I figured it out. According to my calculations (well, my computer's) it's right at the intersection of New York Ave NW and 4th St NW, which is between L and M, and also right where I-395 ends. It's the star in the picture above. So that's sort of interesting.
However, lots of people on the internet seem to be think that the geographic center is under the center of the dome of the Capitol Building, which isn't true. The Capitol Building is the center point of the quadrant system, but it's not exactly in the center - if you look at the picture below, you can see that the NW quadrant is by far the biggest, and NE is second biggest, skewing the results to the north and west of the Capitol. It's a subtle difference of description, but it results in a pretty big difference on the ground.
Even if you consider the original borders of DC, which included Arlington and part of Alexandria, the Capitol dome is still not the geographic center. That geographic center is the circle, which is between Constitution and C, 17th and 18th NW - where the Red Cross building is.
Unfortunately, tons of people have it wrong, including the Washington Post and Brian Williams of NBC News. Lots of various blogs and websites have it wrong too (e.g. here and here. This one's kind of half right - it is the beginning of the quadrants, but that doesn't make it the geographic center. And you can comment on this guy's blog, so I posted about the geographic center, but he seems to have deleted it. I guess he doesn't like his geography skillz being questioned.
Only a few sites have it right, including Wikipedia's article on the Capitol building and this random one from 50states.com. The difference between 50states.com and my calculation probably depends on what you use for the DC border - if you include water or not, etc. I did, because technically the DC border extends to the Virginia shore, not the middle of the Potomac, which is pretty unusual. It also results for some quirks, such as part of the George Washington Parkway and that circle at the entrance to Arlington Cemetery being technically part of DC. So now you know, and knowing is half the battle. I dunno what the other half is.