Folks are digging up a parking lot in Baltimore. What's more, they're asking innocent bystanders for help. With true community spirit, people are pitching in. They claim it's fun.

The parking lot in question -- a few blocks from Harborplace at President and Lombard streets, where once were spaces for 56 cars -- is the site of an archeological excavation. Since early July, scores of volunteers have been attacking the earth with picks, shovels, brushes and trowels. It's the sort of undertaking you'd expect to find in Rome. But what could they be digging up in Baltimore?

Why, a brewery, of course.

"It was the biggest brewery in the country when it was built around 1783," says Elizabeth Anderson, Baltimore's newly appointed city archeologist. "It was started on the site of another brewery dating back to 1761, by a wealthy man from Philadelphia named Thomas Peters. He had served with distinction in the Continental Army and married into the family of Edward Johnson, who was the third mayor of Baltimore.

"Peters thought he could make a handsome profit selling beer to the French and American soldiers who were still fighting in the Revolutionary War. But the war ended before Peters expected it to, just as he was about to open for business. It was kind of a catastrophe at the time."

The brewery managed to thrive, however, through fires, new owners and twists of fate. It joined the annals of American history in 1814, when a neighbor lady named Mary Pickersgill deftly sewed the original Star-Spangled Banner while sitting comfily on the floor of the malt house.

Under the venerable brand name of Clagett's, the brewery made only English ale and heavy beer -- as many as 10,000 barrels yearly -- until forced to shut down by a wave of light German varieties, which was all anyone wanted by 1879. Then beers gave way to biers. The National Casket Company retooled the plant for coffin- making and used it unto death amid the urban renewal asphalt of the early '60s.

The other weekend, Anderson and another archeologist, Charles Cheek, were doing what they usually do these hot summer days. They were laboring under the sun with a dozen loyal helpers, crouching in trenches and carefully turning the dirt.

Marking a grid of five-foot squares with lengths of taut string, they worked under makeshift tents, behind a chickenwire fence blazing with signs announcing, "Archaeology Baltimore," with one at the gate bearing the legend "The Great Baltimore Brewery Dig."

They paused every so often -- because this, don't forget, is Baltimore -- to lead tour groups through the site, give "dig updates" over radio station WCBM, make cold-soda and corned-beef runs to Altman's Delicatessen and blanket the neighborhood with leaflets reading, "The past is just around the corner -- join us."

Al Lewis and his son, Richard, were among those who accepted the invitation. "This is something we can do together as father and son," said Lewis, a barrel-chested fellow with a T-shirt proclaiming, "Beer Drinkers Make Better Lovers. But They Never Remember."

"Oh, I like my beer," he said, standing stoutly in the dust, "but to me, this is like digging into history, or maybe even taking part in history by finding something."

"It's pretty nice," Richard agreed, tugging on his baseball cap from the Stembridge Pirates Little League team.

So far, the diggers have had a measure of success. Here are some of the things they've dug up and identified: foundations of the malt house and cooperage, part of a brick privy to a residence on the site, an inch-tall porcelain doll, pieces of cream ware and Chinese export porcelain from the table of a well-to-do family, shards of a Rebecca-at-the- Well glazed teapot typical of the mid-1800s, the stem of a wine goblet, decorative plaster molding, a ballpoint pen promoting Altman's Deli with a printed proposition ("If the answer is yes, keep this pen. If not, please return the pen, as I am running short"), and -- much to everyone's surprise -- two perfectly preserved bottles, one for wine, the other beer.

They were found by a hardware salesman named Stephen Arey, who's been spending most of his free time mucking about in the dirt.

"I was picking with a hand pick and troweling, but I didn't expect much in the way of artifacts," he says. "Then I saw this wine bottle standing on end against a pillar. It was quite a shock." He uncovered the beer bottle a couple of weeks later. Both bottles were empty.

But Baltimore's activist mayor, William Donald Schaefer, who has been making regular visits to spur the diggers on to greater glory, "told us he won't be satisfied until we find a bottle with beer in it," Elizabeth Anderson says. YOU CAN DIG IT THE GREAT BALTIMORE BREWERY DIG -- At the corner of President and Lombard streets, with tours and hands-on experience offered from Wednesday through Sunday, 10 to 3:30. Call 301/396-1866 for details. HISTORIC ANNAPOLIS -- This Saturday is your last chance until October to take a guided tour of the 18th-century Victualling Warehouse at 77 Main Street, one of several archeological excavations in town. Two other digs, being conducted with the help of a federal grant, are the 1747 Reynolds Tavern at Church Circle and the Charles Street house of Jonas Green, owner-editor of Maryland's first newspaper. Call 301/268-7770. ALEXANDRIA -- Digging is nearly done at the Coleman site on South Royal Street, where archeologists have uncovered 150-year-old knickknacks, but you can still help out in the archeology lab. Call 838-4399. ST. MARY'S CITY -- Or, actually, "St. Maries Citty" as they spelled it in the 1600s, which is when several important buildings of Maryland's first town were erected. Archeologists are currently excavating the 1635 home of Leonard Calvert, Maryland's first governor; the 1634 St. Maries Fort; and the 1645 Second Fort built by Nathaniel Pope, the first American ancestor of George Washington. They don't need volunteer diggers, but you can look and learn, from Wednesday through Sunday. Call 301/862-1634.