Underneath the asphalt streets of Old Town Alexandria there is a layer of brick. Beneath that are cobblestones. Deeper still is the real foundation - dirt and clay of the original streets, laid out according to a plan surveyed 250 years ago by the Fairfax County surveyor, John West Jr., and his young assistant, George Washington.

Through these streets soldiers have marched to four wars on this continent. Washington passed through them on his way to the townhouses of friends, or to worship at Christ Church. Stevedores pushed casks from frigates and schooners along them. And as a boy, Robert E. Lee played on these streets.

Today, at least on weekdays at 8 a.m. and 5 p.m., these streets are clogged with commuters' automobiles - all heading to or from Washington - a reminder that Alexandria, once a major seaport and a city in a league with Philadelphia and Charleston, is a suburb of Washington. And as the spruced up townhouses and shops lining those streets also attest, that role has helped Alexandria recapture the prosperity so elusive since the town's salad days more than 150 years ago.

Since its founding, there have been a few benchmarks for Alexandria vis a vis Washington - not years that were necessarily glorious for the city, but points decisive in crystalizing Alexandria's own identity, or in anchoring her prosperity to the increasingly important metro polis across the potomac. 1749

On July 13, 1749, Alexandria's municipal government was organized.

Since the town was being established on land belonging to the John Alexander family, naming the town Alexandria seemed a fitting way to acknowledge those early settlers.

Alexandria then had nine streets, two public wharves and 66 half-acre lots. Two lots were designated for market square, where city hall now stands, and the remaining ones sold at public auction, fetching an average price of $78 each.

Life in Alexandria must have been simple then. Most families had gardens. They baked their own breads from corn and wheat ground at mills on Hunting Creek and Four Mile Run, and there was plenty of fish - sturgeon, shad, herring and perch - a net's throw from the town shoreline.

Those early families probably lived in simple cottages near the Belhaven tobacco warehouse on Oronoco Bay. The warehouse was owned by a Scottish import firm and operated by three off firm's agents: William Ramsay, John Carlyle and John pagan. 1801

By the time the District of Columbia boundaries were established to encompass Alexandria, the town had weathered a revolution, buried its favorite native son and gained a reputation as a major port.

When Congress assumed actual jurisdiction over Alexandria in 1801, the town was well-established - with 25 taverns, a library, schools, a city museum, a theater, a newspaper, shipyards and a thriving port. Across the river about 200 federal employes worked in a handful of recently completed public buildings.

Early Washingtonians often came to Alexandria, frequently to John Gadsby's tavern and hotel at the corner of Royal and Cameron streets, where Gadsby had developed a reputation as an excellent host.

If the town had a golden age, the early 19th Century was it. Twenty-one wharves lined the shore and seldom were there fewer than 20 square-rigged ships at anchor. Sloops, schooners, brigs and galliots plied their way up the Potomac to Alexandria. Local merchants and mariners owned about 40 vessels that sailed from the port, trading in goods such as salt, plaster of Paris, livestock, tallow candles, rum, sugar, molasses, wine and fruit.

North of the harbor, an area called Fish Town grew up, probably near the site of that first tobacco warehouse. Fish Town was known as a "rough" area of town - a favorite place for magicians. Punch and Judy shows, organ grinders and harlots. It also was a backbone of the town's springtime economy, when the bulk of the Potomac catch was brought in and hundreds of people were employed to salt and pack the fish.

Even though the early 1800s were prosperous times, there were those who craved for more and believed Alexandria's fortunes would rise when it became part of the District of Columbia.

But the hoped for benefits did not materialize. George Washington had seen to it that no federal buildings would be constructed in his home state. And perhaps for this reason, real estate values, which were rising across the Potomac, fell 25 percent in Alexandria after Congress assumed jurisdiction. 1846

On July 2, 1846, Congress yielded to the desires of the disenchanted District residents in Alexandria and ceded the Virginia part of the capital back to the state.

Cast free again, Alexandria set off to regain the momentum of her turn of the century prosperity.

But the goal proved elusive. Other ports had gained prominence, and Baltimore soon supplanted Alexandria as a major harbor. The death knell for Alexandria's sea trade came when the Baltimore and Ohio Railroad was founded.

One attempt to revitalize the harbor, by transporting coal to Alexandria from Cumberland. Maryland, was made via the Alexandria Canal, an expensive and ill-fated project, which ran across the Potomac on an aqueduct and joined the C&O Canal in Georgetown.

The project had a cost overrun of more than 80 percent and was finally doomed by the railroads, which proved to be cheaper and quicker than shipping by canal.

One trade was flourishing - slaves. At 1318 Duke St., a building which still stands, the firm of Franklin and Armfield and later Price, Birch & Co., traded in Negro slaves, who were kept in rude huts and pens around the building until they could be sold.

But there were a number of free blacks in Alexandria, too - 1,168 according to the 1820 census - many of them craftsmen and tradesmen. 1880

Alexandria's old style of life had begun to fade, but on June 19, 1880, that style was officially laid to rest when the town council prohibited the keeping of swine within the municipal limits. In 1881, Southern Bell Telephone and Telegraph Co. began putting up poles and wires.

Progress had arrived for the 13,659 Alexandrians, but prosperity was still decades away.

Alexandria, which was occupied by Union troops from 1861 to 1865, had emerged from the Civil War like many of her Southern sisters - almost flat broke. The Alexandria Canal had been an economic disaster, and to help pay municipal debts, the city was forced to sell, for $100,000, all its stock in the four railroads Alexandria had helped build.

Much of the city's charm and sophistication were destroyed during the war years. Junk shops lined King Street; Gadsby's fine old tavern had been sold and turned into a tenement. 1933

In 1933, the first steps were taken to transform the rather dowdy, struggling town into what Alexandria is today - a modern yet historic city, and one of Washington's principal suburbs.

Franklin Delano Roosevelt had just come to the White House, bringing with him a New Deal and the beginnings of real growth in the federal government.

According to Alexandria's old-timers, the New Dealers "discovered" Old Town and began restoring the federal and Victorian townhouses there.

The fledgling interest in Alexandria as a convenient and charming bedroom community for federal workers was a hint of things to come. But only the most far-sighted could have interpreted the signs. From all appearances, the town still was down at the heels - struggling, like most American communities, through the Great Depression.

In January 1933 the local Ford Motor Co. plant, employer to 125 people, closed. In an effort to save money, the city council cut the municipal budget from $17,000 to $12,000. And so many people turned out to get free shoes, collected for the poor by the local Kiwanis Club, that the police had to be called to keep order.

In 1930, Alexandria's population was 24,149. Clubs, like the Kiwanis, the Elks and the Freemasons were strong. An historical society had been founded, and its members were devoted to encouraging the restoration and preservation of the town's oldest structures.

There were about 5,500 homes in the town, and you could rent one in Old Town for $42.50 a month. 1978

The seaport years seem far away. An occasional barge filled with newsprint comes inot the Robinson terminal dock at the foot of Wolfe Street, and pleasure craft are moored where there once were square-rigged vessels. The Potomac Catch, so plentiful a 100 years ago, has been reduced to a few catfish.

Most of the means to economic prosperity - the sea, the railroads, industry - that Alexandrians looked to after the 1800s, never materialized.

But by most economic yardsticks Alexandria is thriving.

The City Manager's Annual Report submitted to the council last fall, showed a healthy unemployment rate of 3.2 percent. The real estate tax base has been growing steadily, jumping 13.6 percent between 1976 and 1977. And the median family income, while lower than that for the metropolitan area, was $14,100 for 1976.

Most of the housing expansion has been in the city's west end; "Condo Canyon," near the Shirley Highway corridor, and in Old Town, where townhouses and condominium developments, such as Watergate of Alexandria, are filling much of the vacant land.

The key to Alexandria's present economic health, unsuccessfully sought for so long, is a new kind of suburbanization - not sprawling acres of subdivisions, but one where you can see the lights of Washington from an 18th floor living room window.

At the same time, Alexandria has been busy capitalizing on the mullion-windowed quaintness and sense of place in Old Town - encouraging the area to grow commercially more like Georgetown, and at the same time, attracting residents who like urban life at a slower pace.

But City Manager Douglas Harman is guarded in his predictions about Alexandria's future prosperity. Although he says trends are favorable, the city has some troubling problems - primarily its relatively high proportion of poor people.

Whether the fragile, and crucial, balance between economic growth and social factors can be maintained probably holds the key to Alexandria's future, according to Harman in his annual report for 1977. And that, many feel, is a problem that may be more difficult to deal with than declining ports, an ill-fated canal or a disastrousCivil War.