For this little community, which once proclaimed itself "City of the Future," 1984 was turning out to be another year of declining fortunes.

Job layoffs pushed the unemployment rate to 20 percent. Squeezed by low milk prices and high debts, 35 dairy farmers auctioned their land. City bridges sagged, and the aged water system was leaking badly. Two schools remained closed for want of students. A third of the area's hospital beds were empty. A permit to build a house rated a story in the Watertown Daily Times.

Then, on Sept. 11, good news hit this upstate New York city with the force of one of its nor'easters: The Army had picked Watertown for the birth of a base. A depressed town suddenly caught what former mayor Karl R. Burns calls "gold rush fever," with officials scurrying to find housing for 5,000 construction workers, "big city" developers breaking ground for a 500,000-square-foot shopping mall, fast-food chains sprouting on historic Arsenal Street and bankers lining up to finance a five-year building program whose projected cost of $200 million a year exceed Watertown's annual budget tenfold.

"It used to be all gloom and doom here," said Mary Parry, executive director of the Chamber of Commerce. "Now we're headed for a windfall."

Far from Washington and the esoteric weapons competing for President Reagan's $300 billion defense budget, the Army's decision to convert a summer reserve training camp, Fort Drum, just outside Watertown into the headquarters for the new 10th Light Infantry Division shows a different side of military spending, one that touches Main Street, U.S.A.

It is in Washington, however, that a base is conceived and becomes virtually a lifetime dependent of the national treasury -- or, in the parlance of critics, a chunk of the Pentagon's meaty pork barrel.

It is in military bases where the interests of defense spenders and the toughest skeptics in Congress converge. To lawmakers, the lure of jobs and capital to districts that house military installations is too powerful to offset the hard facts: Most of the 4,000 military facilities in the United States are costly white elephants.

A presidential panel concluded in 1983 that phasing out just 50 "unnecessary and inefficient installations" would save taxpayers $2 billion a year, but it added that "the subject is politically painful to pursue."

At about the same time, the Army was laying the groundwork for Fort Drum. Chief of Staff Gen. John A. Wickham Jr. approached Congress in January 1984 with plans to form a light infantry division of 10,000 soldiers mobile enough to move quickly to crises abroad.

Nine months later, Fort Drum was chosen as home of the new 10th Division, despite Army projections of higher development costs there than at competing military installations in Alaska, Washington state, Kentucky, Georgia and California.

The Army reasoned that Fort Drum was the only place large enough to contain the entire division.

Pentagon officials point out equally compelling political considerations. They say Fort Drum benefited from intense lobbying by the New York delegation, led by Rep. Samuel S. Stratton (D-N.Y.), then considered a strong candidate to become chairman of the powerful House Armed Services Committee. Contributing political muscle were Rep. Joseph P. Addabbo (D-N.Y.), chairman of the House Appropriations defense subcommittee, and Rep. David O'B. Martin (R-N.Y.), a member of the Armed Services Committee whose congressional district includes the base.

Torn by conflicting power centers -- Sen. Ted Stevens (R-Alaska), chairman of the Senate Appropriations defense subcommittee, fought hard for the base in Alaska -- the Army proved obliging: It announced plans to base the second light infantry divison in Stevens' state.

"By going with Drum, the Army built a constituency with the New York delegation," a senior defense official said. "But they knew they'd have to mollify Stevens and could get another base in the process."

Four hundred miles from this Capitol Hill intrigue, in the "north country" wedged between Lake Ontario and the St. Lawrence River, Watertown learned that the Army was coming and instantly developed a "Fort Drum high," City Manager Karl Amylon said. "Everyone was running around in a euphoric state."

"Nobody was thinking of the problems then," he said.

How this quaint town of 28,000 people -- conservative, Republican and 99 percent white -- prepares for the invasion by 1990 of as many as 50,000 soldiers and their families, civilians and construction workers, including thousands of urban blacks and Hispanics, is the story of a community in transition.

Local surveys show overwhelming popular support for Fort Drum, which many people think will bring jobs and money to Watertown -- "a shot in the arm," in the words of ex-Mayor Burns.

Some farmers have sold land to developers at 10 times the price they could have received last year. Labor unions hope to fill many of the 6,000 jobs expected to be created by the base. Merchants on Public Square have put up new signs and cleaned the brick on their storefronts in an effort to cash in on the estimated $400 million a year in consumer sales expected to be generated by the base by 1990. Car dealers are expanding lots for an anticipated sales boom of 4,000 cars a year.

Not everyone shares the boom-town spirit, however, and even the biggest boosters fear the blight of strip joints, drugs, hustlers and crime typical of military towns.

"With an infantry division, you're going to get the bottom of the barrel socioeconomically," said Jack Scordo, a local lawyer. "You're going to have racial problems, massage parlors, strip development. You're going to see streetwalkers, a lot of fights, a lot of riffraff. There'll be bail bondsmen on every corner. We're going to be an occupied town."

Officials say that the dark side of Fort Drum is an inevitable byproduct of growth -- James Merritt, chairman of the Fort Drum Steering Council, calls it "culture shock" -- although zoning laws are being rewritten to contain the sleaze factor to certain areas.

The steering council has established several task forces. A medical group is recruiting nurses and obstetricians for an anticipated boom of 1,000 additional babies a year, an unusual turnabout for a city that has been losing residents for years.

An educational panel is studying the need for bilingual teachers.

Police Chief John Cascanette has asked the city for a 30 percent increase in personnel, 12 new cars and stun guns to handle what he predicts will be a growing crime problem.

The city plans to correct what Amylon calls "20 years of neglect" by patching its water system, shoring up its bridges, finding a new landfill and upgrading its dilapidated power system. But no one is sure how to finance the improvements.

Fort Drum is planning to house most of its soldiers off the base, and the Army is negotiating with private developers to build 1,400 garden apartments among the old Victorian-style homes of Watertown and its environs.

Once a thriving paper-mill town named after the hydropower supplied by the Black River, Watertown fell on such hard times four years ago that its "City of the Future" signs were removed.

"I think it's time to put the signs back up," Burns said.