Unless I've somehow overlooked another one in town, there is onlyone boulevard in the District of Columbia--MacArthur Boulevard, named by act of Congress during World War II out of a superabundance of admiration for Gen. Douglass MacArthur's exploits in the Southwest Pacific Theater. It's no knock on MacArthur to wonder why Congress didn't find some other arterial to honor his counterpart in Europe, Gen. Dwight D. Eisenhower. A modest suggestion to the D.C. City Council, which now has streetnaming power: why not assign his name to the Center Leg Freeway, which carries I-395 beneath the Mall and north toward New York Avenue. Heaven knows it needs a better name!

MacArthur Boulevard's original name was Conduit Road, so called because the city's major water pipeline from the Potomac River to the Georgetown Reservoir is located beneath it.

We've been asked to explain the District's system for naming its trafficways. Here's a primer:

Roads, such as Columbia, Blair, Foxhall, Lincoln, Military, River and Benning roads, are thoroughfares that existed before the modern street system was laid out. They tend to meander across the cityscape.

Streets, lettered or named, are the modern east-west trafficways, and, numbered in most cases, are their north-south counterparts.

Avenues, named for states and territories, began as diagonal thoroughfares interconnecting the circles and squares of the original L'Enfant Plan for central Washington. As the District road system expanded and the number of states multiplied, some outlying thoroughfares (Nebraska, Alaska, Nevada) got avenue designations, too. Some, like Wyoming Avenue, by rights should be streets. And some early roads were converted into avenues; Georgia Avenue, for instance, was originally the Seventh Street Road.

Parkways, freeways, lanes, alleys, drives and terraces (have any other designations been overlooked?) need no explanation.

Three big states have no avenues here. They're California, the nation's most populous state, which has two (count 'em) insignificant California streets in widely separated parts of town; Washington, which presumably would create great confusion, and Ohio, long lacking any local recognition but rewarded with a riverfront Drive in the 1940s thanks to the late Rep. Thomas A. Jenkins (R-Ohio).

There's one avenue that has a different name on the city's official street maps than it has on the street signs. Who knows which one?