A picture, they say, is worth a thousand words. In the case of a zoning map such as Washington's, ten thousand words might be a fairer ratio, given the accompanying 300-page ordinance.

Washington's zoning map is a patchwork quilt of patterns and shapes. Like a real quilt being used year after year, it has been stitched together, usually piecemeal, with new layers of zoning sewn into it every so often as old zoning spots wear out.

Looking at the map in overview, you can see dominant, overall patterns of land use that conform generally to your impression of the city's transportation, neighborhood, and physiographic patterns.

Large, homogeneous, single-family residential districts -- R-1 zones -- dominate much of Northwest and the fringes of Northeast. Row dwellings -- R-2, R-3, R-4 zones -- cover most of Georgetown, Capitol Hill, Anacostia, and near Northwest, penetrating close to the city's central core.

The R-5 apartment zones, ranging from low (0.9 FAR) to high (6.0 FAR) density, seem to be the most scattered and randomly located. They appear often as isolated, irregularly shaped spots intermingled with other residential and commercial areas.

Industrial districts -- C-M-1, -2, and -3, plus M -- mostly follow the alignments of railroad rights of way. They adjoin harbor or waterfront facilities along the Anacostia and sections of Northeast near North Capitol Street, New York Avenue and Bladensburg Road that have a long history of industrial use.

Of all the two-dimensional land-use zones, the commercial ones perhaps relate most easily to the three-dimensional urban forms that we habitually see and recognize. The C-2 and C-3 zones, representing community-scale retail and commercial services, tend to be linear, serrated-edge strips of varying length defining many of the radial avenues: Wisconsin, Connecticut, Georgia, Rhode Island, Pennsylvania. Spots of C-1 zoning dot the map to provide neighborhood convenience shopping.

Like some R-5 apartment districts, C-2 and C-3 zones occur in shapes, sizes, and locations that seem happenstance. This is inevitable in a zoning map reflecting patterns of past, unplanned use molded by private property initiatives. Recall that the District's first ordinance was adopted in 1920, a time when many of today's land uses already were established.

C-4 and C-5 zones appear only downtown, defining the central business district and the Pennsylvania Avenue Development area. The SP zones have been imposed in and around downtown to mark properties slated for mixed uses near major intersections, circles, squares, or in conjunction with special facilities such as Judiciary Square or the White House.

In recent years, unique zoning classifications have been developed for unique areas. The mixed-use waterfront zones, W-1 to W-3, were invented and applied only to the Georgetown waterfront south of M Street. The high density CR (commercial-residential) zone, with its allowable FAR of 6.0, its 90-foot height limit, and its provisions for mixing uses in single buildings, exists only on blocks in the West End adjacent to Rock Creek Park and between M and N streets.

Still on the map is the UR category, "urban renewal," which covers much of Southwest. It was adopted in the '50s and '60s during urban renewal's heyday and encompasses both commercial and residential uses.

The diplomatic overlay, D, predominates in the residential zones along Massachusetts Avenue and appears on Connecticut Avenue and 16th Street. The HR overlay ("hotel-residential incentive district") has been mapped onto commercially zoned properties west of Union Station and around the Convention Center and Mt. Vernon Square. This is a direct manifestation of the District's economic policies aimed at increasing downtown convention business, tourism, employment and tax revenues.

Only a close look at each section of the zoning map reveals its jigsaw puzzle nature. Zoning boundaries between districts zig and zag, curve, cut through blocks, or slice down the middle of streets, alleys and avenues. Some are incredibly convoluted and irregular, like the proverbial "gerrymander."

How and why each separate piece came to be where it is, to have the shape it has, or to convey its particular use rights to its particular site, defies easy analysis. Time, circumstances, and acts of will produced the map, and not all the map-making and zoning decisions were logical and far-sighted.

Last year, the District adopted a new comprehensive plan, including a colorful land use (not zoning) map. It should be no surprise that the land use map looks a lot like the zoning map.