At first the Navy did not seem to change life very much. Planes screamed across the Patuxent River from the air test station, but down below the residents of St. Mary's County planted tobacco and soybeans and worked the waters for fish and crab and oysters as they always had done.

The Navy brought its camp followers, of course, when it moved here in 1942. The ramshackle bars and strip joints quickly made "The Park" the liveliest crossroads in the county. But that was not saying much when the only competition was the quiet county seat of Leonardtown.

In recent years, however, the Navy has wrought controversial changes on the county, a peninsula between the Potomac and Patuxent rivers. It has prompted a surge in housing and business development, the wheeling and dealing of property, unprecedented growth and, in the latest turn of fate, an investigation by the Maryland state prosecutor into the county government's development actions.

The main role of the 6,384-acre Patuxent Naval Air Test Center is developing and testing military aircraft and the sophisticated equipment that goes in them. Starting about 10 years ago, the Navy began contracting out much of the computer and engineering work, and defense firms started sending computer experts and engineers to this tiny town 60 miles south of Washington.

They set up shop in rented rooms at the Belvedere and other motels, and when business kept booming they started building and leasing their own quarters. Last year, around $217 million in contracts was awarded through the naval station, and more than 70 defense contractors were located in the county.

Now a visitor is surprised to see gleaming, modernistic office buildings rising amid the roadside filling stations and vegetable stands, and surprised to be caught up in rush hour traffic in downtown Lexington Park. New high-tech names like Bendix, Tracor and Dynamac have become part of the local lexicon.

When Jesse Hawes came to St. Mary's County six years ago to run a fledgling high-tech firm, there were a few fellow Navy camp followers, but not much else. "The only time you have a traffic jam is 10 o'clock on Saturday morning when all the farmers come to town -- and that lasts 10 minutes," he recalls telling his wife after he first arrived. "That's not true now," he said recently. "We are having problems with traffic."

Since 1979, the number of civilian workers in this county of 65,000 residents has risen from 15,321 to more than 20,000 and the amount of office space in the county has more than doubled. In 1977, fewer than 800 people worked for defense-related companies. Now those firms have around 4,000 employes.

The base itself has about 3,800 military personnel and an equal number of civilians.

North of Lexington Park, houses are being added to the giant Wildewood development -- which already has about 400 houses -- at the rate of a hundred a year, with more than 2,000 planned. A new shopping center is being built next to it. Nearby is the new Wildewood Industrial Park and a new privately owned St. Mary's Industrial Park. Also nearby is the county airport, where daily flights to Dulles and BWI will soon begin. Across Rte. 235 -- which is being widened to four lanes, the Dean's Industrial Park is planned.

Farther south is the new Veda Corp. Building -- the firm sells computer-related services to the Navy -- and another office building is going up beside it. New apartment buildings are going up opposite the new Bendix, Sperry and ManTech buildings. At almost every corner of the "Golden Triangle" formed by the main highways around Lexington Park there is construction.

County officials say all this has been good for the county, but some critics say it has been good mostly for county officials. Commissioner Larry Millison is one of the largest landowners and developers in the county. Commission president George Aud is a part-time real estate agent and investor. Commissioner Richard Arnold has been involved in several development projects. Commissioner Ford Dean is a mortgage banker. County administrator Ed Cox is a part-time real estate agent. Planning Commission Chairman Joseph M. Gough is president of the First National Bank of St. Mary's County, which lends money for development.

"One must look beyond the appearances," commissioner Dean said. "St. Mary's has 65,000 people . . . . Sooner or later, unless you happen to be an officeholder with absolutely no other interests, you are going to find the situation where you have a conflict.

"Has there been any lack of concern for the public interest? No," Dean added. "That's not the case. Has there been a conflict between the public interest and the private interests in real estate development? I can't speak for every single individual, but I'd say generally no."

"It's short-term gain for some people," said James Dobry, a contractor in the county who has done some residential development. "I think they are trashing the county in a lot of ways." Development is not sufficiently controlled, he said, and the suspicion is widespread that approval depends more on who you are and who you know than on the merits of the proposal itself.

The time has come, he said, for St. Mary's to replace its county commission form of government with a county executive and council such as that in Prince George's and Montgomery counties. A separate county executive with the power to veto county council action would provide the separation of power and safeguards that St. Mary's needs, he said.

Many critics of the county commissioners point to the new Veda Building as an example of how entangled the commissioners are in the land dealings they are meant to supervise.

The building, built to house a high-tech firm near Lexington Park, was constructed on land sold by commission president Aud. The developers turned to commissioner Dean -- the mortgage banker -- for financing. Commissioner Millison also had his connections with Veda, for he was the firm's previous landlord.

When the developers applied for industrial revenue bonds last year, the problem of conflicts became apparent. Millison did not show up for the meeting -- saying afterward he could not have voted because of potential conflicts. Dean excused himself because of his work financing the project.

If Aud, who completed his land sale for the Veda property only the day before, had abstained, the commissioners would not have had the three-member quorum they needed. Aud had gone to the county ethics commission, which told him he could vote on the Veda bonds because his land deal was already completed and a conflict no longer existed.

Aud and two other commissioners voted for the bonds, and the gleaming white and silver building that resulted stands on Rte. 235 as a monument to the high-tech prosperity that the Navy has brought St. Mary's County.

To investigators working with the office of the state prosecutor in Towson, the building apparently suggested much more. When a new Circuit Court grand jury was convened in Leonardtown in September, prosecutors sought and obtained more than 100 subpoenas for documents relating to the county's land and development dealings, including a host of documents relating to the Veda project.

Prosecutor Stephen Montanarelli acknowledges his investigation concerns the county's development dealings but refuses to go into further detail.

Now, unknown persons appearing at County Commission meetings are sometimes rumored to be undercover state troopers. Planning Commission chairman Gough said he knows of some business persons who have abandoned development plans because they fear accusations of conflict of interest. Other officials say business persons have told them they are no longer interested in serving on government committees because of the investigation.

But most people in St. Mary's County don't seem terribly interested in the investigation and the Veda Building controversy, and few say it is likely to amount to anything. "Nobody talks about it or understands what it's all about," said a legal secretary who works in Lexington Park. "People see this building and say, 'Hey, that looks nice -- like right out of Dallas.' "

"You can't keep anybody from holding office because of their wealth or their property owning, I guess," said John Lancaster, a county school board member who ran against commissioner Millison in the last election. He said he sees nothing wrong with the Veda deal or the commissioners' real estate interests. The development boom that high-tech has brought to the county is no secret, he said, and you do not need to be a commissioner to take advantage of it.

But the investigation has stoked debate over how well the county is responding to the development boom -- whether the county is rightly taking advantage of opportunities offered by high-tech contractors, or whether it is greedily accepting development regardless of its price.

Jack Whitten, a critic of many county-approved developments, says it is too easy for building projects to be pushed through without public input. "They need to change the whole atmosphere so that the public isn't being treated as an adversary of the county government and the applicant," he said. "The county government should be neutral, but they're not."

Gough, the planning and zoning commission chairman, disagrees. Planning meetings are open, he said, and people can find out what is going on and have their say. "I don't think the county has sold out to developers," he said. As a planning commissioner, he said, he might have "a better feel" for the pulse of the county but no insider information. He predicted that the spurt of development will slow before long and that criticism of development will fade.

"It's a whole new ball game for people here," said Joseph Mitchell, the county's housing and development director. County government has taken "a conservative position" in the face of the development boom, he said, concentrating on trying to match businesses interested in St. Mary's with potential developers and land sellers rather than getting involved more directly.

Edward Thomas, an assistant secretary of state planning, however, said government officials in St. Mary's County "weren't ready in any way, shape or form" for the development spurred by the naval base.

Thomas says growth has been uncontrolled. Waterfront property has been eaten up by housing developments, he said, while business development is packed in along roadsides without large-scale, long-term planning. The high-tech firms were so anxious to be near the air test station in St. Mary's that the county could have spelled out stringent terms for development. Instead, he said, the county has "subjugated itself" without needing to do so.