On an interstate highway near Houston, there is a gas station and convenience store that is unexceptional in all but name. It is called, incongruously, The Corner Store.

In nearby Galveston there is a vacant lot on the corner where Jules' Food Market used to be. This real corner store sold the convenience items--sodas, snacks, toothpaste--and a general line of groceries that included, according to the sign in an old photograph, "fresh produce and fresh meats."

Like most such stores in Galveston, Jules' had a shed-roof wooden canopy reaching from the building out to the edge of the street. People would gather there in the afternoon, sitting on the steps.

"They come here because it's cool," proprietor Jules Albert told an interviewer back in the '70s, when the store was still standing, "and they can sit there whether it's rain or shine and, you know, enjoy themselves."

In the interstices between these two realities--the genuine article in Galveston that is now only a memory, and the sad highway approximation with the generic name (and not a corner in sight)--lies the story of an everyday American institution that once was so common that nobody gave it half a thought.

"The Corner Store," a new exhibition on view until March at the National Building Museum, celebrates this institution, tersely catalogues its decline and pleads that the buildings be saved and put to good use.

Galveston is the focus of the exhibition because that is where the guest curator, preservationist Ellen Beasley, immediately fell for the homely yet unusual commercial structures at almost every intersection.

The Galveston stores are noteworthy for the prevalence of a single architectural feature--shed roofs extending out to the curb line, supported by wooden posts. Such shedlike extensions are common throughout the South, but in no other city were so many corners so marked.

Otherwise, the story of the Galveston stores is similar to that of all American cities, including Washington. The exhibition--made up largely of photographs but also including maps, documents, paintings and objects such as a delivery bicycle--is amplified with a number of examples from all over the land.

Corner stores--especially corner groceries--became ubiquitous in American cities because they were needed and convenient, and they fit the typical urban geometry.

Most of our cities were laid out, like Galveston, with a gridded pattern of streets. Intersections were prized locations because corners are where people cross paths--potentially, any given corner could draw nearby customers from four different directions.

Consequently, corner stores dotted residential areas. In 1890 Galveston, for instance, there were 5,853 households and 233 retail grocers. One store, that is, for every 25 households--not much of a customer base. Yet these groceries were able to thrive.

People walked to the corners, of course. As cities expanded during the 19th century, the increased distances between homes and central food markets made daily shopping trips less and less feasible for the average citizen. Keepers of the neighborhood corner store thus became the middlemen--or, frequently, middlewomen--in this system of domestic supply.

A principal reason for the proliferation of such businesses, in addition to logistics and location, was technology--or, rather, the lack of it. The absence of a widespread, reliable means of refrigeration, especially in the home, made daily food shopping a necessity. Small-store keepers would get up early and head for the larger markets, bringing fresh foodstuffs back to the neighborhood.

Yet another cause for the success of corner stores combines economics with sociology. It did not take a whole lot of money to start up a little grocery. Human capital was more important--some smarts, ambition, a willingness to work long hours and, most important, a family to help with the work at low to zero wages.

For just these reasons, in city after city corner groceries attracted many immigrant proprietors. For a thrifty, hard-working couple with kids, whether immigrant or not, such small businesses could be a major first step on the ladder of American promise, offering a measure of both independence and security.

Architecturally, the corner shops tended to adapt to the regional habitat in materials, color and style. Generally speaking, architects were not involved in their design. Rather, the buildings were part of the local vernacular building system, constructed by contractors at the same time nearby houses or apartments were going up.

Despite regional differences, however, there is a similarity to these buildings across the continent. In form and plan they are adaptations of the familiar Main Street pattern of ground-floor retail spaces with living quarters above.

This arrangement explains the attractiveness of such stores to families. Moms and dads in effect could more or less do two jobs--selling food and raising children--at the same time and in the same place.

The living-working combination also aided builders trying to fit such commercial structures into the residential surround. Although there always are some markings of commerce--chamfered corner entrances, signs, display windows, those Galveston sheds--the buildings generally look a lot like the residences in the neighborhood.

Corner groceries are still with us, of course, but in vastly dwindling numbers. The exhibition does not shed much analytical light on this process of decline, which is unfortunate, because closer attention to reasons for the decline might strengthen proposals to halt or reverse it.

In any case, the story is familiar in outline. Improvements in refrigeration both at home and in the marketplace affected the daily rhythms of working, shopping, tending home. Increases in personal mobility--above all, via the automobile--greatly changed shopping and living patterns. Ever more super supermarkets continue to make it difficult for small groceries to compete. Bland convenience store chains ratchet up the pressure. Postwar suburbs with their curvy streets eliminated right-angled corners and, for good measure, forbade commercial infringements in areas of residential bliss. Many city neighborhoods followed suit.

Washington, by the way, more or less mirrors the national story. There are survivors in D.C. neighborhoods such as Georgetown, Capitol Hill, Petworth and others, but definitely fewer than there were 20 years ago. It is hard to say which is more depressing--a boarded-up corner grocery or one that has been transformed into a corner liquor store. There are plenty of both.

It is enough to make one wonder if much need or desire remains for an "institution" that many of us tend to cherish more in the abstract than in reality. Yet there is no question that the sight of a boarded-up corner grocery strikes a chord of sadness in the soul.

It is different even from the sight of a boarded-up house--though both are repositories of memories and stories no longer to be told, the stories of the corner store were more public than private. They were stories shared by many in the neighborhood, and their absence thus is felt all the stronger.

Corner stores were--and still are, to a diminishing extent--sources of an everyday kind of sociability that is getting harder and harder to come by.

Writer Eudora Welty, reminiscing in a Bicentennial issue of Esquire magazine devoted to "Great American Things," described childhood visits to a nearby corner store: "I knew even the sidewalk to it as well as I knew my own skin. We children thought it was ours."

Galveston corner store operator Mary Stiglich, interviewed by Beasley back in the '70s, matter-of-factly said, "Lots of my customers say they like the atmosphere of my little store. We are all like a family, and they come here, and we talk and visit."