Until last year, this was little more than a wide spot on Rte. 31 south of Nashville.

Now it is awash in out-of-town financiers, developers, planners and profit-seekers. For Sale signs adorn farms, roadside stands and houses along major highways for miles in every direction.

Real estate prices have skyrocketed. Rolling meadowland that brought as little as $800 an acre barely a year ago has gone for as much as $35,000. A common price is $15,000. The price of the average house has risen 15 to 20 percent since last summer.

The greening of Spring Hill -- population 1,200, for the time being -- is the result of the General Motors Corp. decision to plow under parts of Haynes Haven, a 2,000-acre farm here, for its $3.5 billion Saturn complex. The site was dedicated today with a hoisting of flags on the white-columned antebellum-style mansion, as local residents joined company officials beneath a revival tent to watch their lives change.

The plant is expected to employ 6,000 people and have an eventual annual payroll of $200 million. The onslaught of outsiders with big plans and big checkbooks grew so heavy some months ago that the City Council and the rest of the city government had to move out of the volunteer fire department into a double trailer, provided by Saturn Corp., near the elementary school.

"We didn't have but a 14-by-14-foot room in the fire hall," said Mayor George Jones, who bears much of the burden of the extraordinary opportunities and problems suddenly confronting his community.

"They got so crowded they were doing business in the bathroom," one woman said.

But the gift of the trailers turned out to be a mixed blessing: The school board is worried that the endless traffic swarming around them endangers the students' safety. It has given the town two years to find a better place from which to govern.

Waiting hopefully for that move is a group of Texas and Tennessee developers that snapped up a 170-acre tract beyond the school on the south side of Spring Hill, adjacent to the Saturn site. They are planning a $250 million commercial and residential center.

"The amount of money is unreal," Jones said of the proposed development, Town Center at Spring Hill.

For now, the center is just a canvas banner atop two poles in a pasture near the school, but its president, Larry Atema, says a spot is reserved in the project for a municipal government complex. No decision has been made, but Jones, a lumber dealer and private contractor who moved here from east Tennessee 25 years ago, said that he is confident it is the right spot for the future.

The town is to receive more than $1 million from Saturn Corp., GM's first new division in 68 years, as a payment in lieu of taxes for the new town hall, huge stakes for a government that in 1985 had a total payroll of two policemen, two water and sewer inspectors, one full-time and one part-time secretary and a part-time judge. Big money has arrived, spinning the same get-rich dreams that the country-and-western balladeers sing about at the Grand Ole Opry, 30 miles to the north.

At today's dedication, Saturn officials still were not saying what the Saturn will look like, how much it will cost, when the first one will roll off the assembly line -- or even when factory construction will begin. Saturn President Richard G. LeFauve said that most of the major production commitments have not been made and that schedules are not the primary concern.

"This car has to be right in quality, delivery and cost," LeFauve said of GM's attempt to beat Japan's small-car makers at their best game.

The project may still be on the drawing board, but its impact is building: Lois Watkins paid $20,000 for the Cedar Inn restaurant on Main Street in November 1984 and turned down a $65,000 offer after Saturn chose its site. She gave in recently for $186,000. Perhaps fittingly, the homey eatery is being turned into a real estate office.

Spring Hill, on the northern border of Maury (pronounced "Murray") County, for months has been annexing territory in Maury and neighboring Williamson counties.

"The only thing that's changed here is annexation," said City Recorder June Quirk with a laugh, calculating that the 12-square-mile city has added "several thousand acres" since the Saturn announcement last summer. Annexations are initiated when residents in contiguous neighborhoods petition for inclusion in greater Spring Hill.

School Supt. Billy Hobbs, facing a probable doubling of the 9,200 pupil enrollment in the next decade, says he is "a little frustrated" trying to predict where to build schools.

"People are going to live where they want," he said. "But we just can't wait and see what happens." There is already crowding around Columbia, the county seat to the south, where James K. Polk, a dour, craggy-faced frontier lawyer, lived for many years before becoming the nation's 11th president in 1845.

Hobbs and his school board are planning a 460-pupil high school for Spring Hill, the kind of forward step that Gov. Lamar Alexander (R) praised at today's dedication. He said Tennessee's emphasis on education was a crucial factor in winning the Saturn site.

"Saturn's going to change the face of Maury County," said Hobbs, a veteran high school principal who became county superintendent barely a year ago. The newcomers "are going to have different needs and desires from what may be our conservative demands."

But he sees opportunities in the changes ahead. "Our schools are generally above average. We're going to be able to move even more in the direction of excellence."

Anticipating such developments, Maury County residents have begun to worry that outsiders' voices will be more decisive than theirs in how the area looks and grows. Jones predicts that within a few years, no local citizens will own major tracts in the vicinity.

"It's hard to believe the changes that are coming. No one likes change," one resident said at the dedication. "But change is coming."

Anne Sparkman, who comes from nearby Culleoka (meaning Sweet Water) and sells real estate for a local firm, said she is confident "we're going to maintain what we've got" in the face of the thousands of newcomers destined to move here in the next decade. They will find, she said, "an easier pace, a whole attitude of life I like."

Asked how townspeople will preserve that pace, that attitude, she smiled.

"By showing them we've got what they want," she said.