The Frenchman Pierre L’Enfant (literally, Peter the Child) designed Washington, D.C.’s street system. Apparently he was drunk at the time. Here is how it works (?). First, there is a directional system with Capitol building as the zero point. The Capitol is directionally centered, facing west (or east, depending which side you think is the front). Anyhow, if you draw four lines at right angles from the Capitol following the four points of the compass, the city is divided into four segments which are named for their compass location in relation to the Capitol– NE, NW, SE, and SW. Most places of interest to tourists are found in NW. With a few exceptions close to the Mall or to the Capitol, stay out of SE, a very dangerous neighborhood.
Next, L’Enfant imposed a grid street system on the compass quadrants. Streets running north-south were
sequentially named with numbers, with 1st St. being the north-south street closest to the Capitol that did not dead end at the Capitol. Applying the compass grid, there are two 1st Streets, 1st NW, and 1st NE. The White House is at 16th St NW, 16 blocks west and to the north of the Capitol.
L’Enfant named the grid streets running east-west according to the alphabet. First come streets with letter names, like C St SW. Upon reaching the end of the alphabet, street names start over alphabetically with one syllable words. Then come a set of alphabet two syllable words, and lastly, three syllable street names. Some people claim to be able to understand even the three syllable streets. We lived there for 25 years, I never got it.
But wait! There’s more! Next L’Enfant laid out 13 avenues named after the 13 original colonies running at angles to the number/alphabet street grid. This is why Washington, D.C. has intersections where as many as six streets cross. The Avenues tend to radiate outward from the Capitol and the White House, but that is not information that will help you get around. It only helps explain the confusion. If you know what you are doing, the avenues serve as short cuts, but if you trying to follow one of the letter or number streets, odds are that sooner or later, an avenue will cut across your path and throw you off course.
The White House faces Pennsylvania Ave. A line extended straight out the front door of the White House is an extension of 16th St NW. Thus, the address of the White House is 1600 Pennsylvania Ave NW, a location north and west of the Capitol building on Pennsylvania Avenue where it intersects 16th St. NW. This ‘logic’ can be applied to all addresses within the city limits.
Finally, just to confuse matters, the first four streets running east-west from the Capitol were given other historical names, Madison and Jefferson for the two inside the Mall, and Constitution Ave. and Independence Ave. for the two streets defining the north and south boundaries of the Mall.