Austin P. Renn was a young man in the spring of 1928 when he brought his bride to this fertile, sparsely settled valley in Frederick County between Sugarloaf Mountain and the Catoctin Mountains.

The roads were dirt, he recalled, but the air was pure and the earth was bountiful. If a man wasn't afraid of hard work, he could make a decent living raising corn or cattle.

"This was a beautiful area when we came here and I've spent the best years of my life here," said Renn, who is 82.

But now, after 52 years of raising heifers and corn on his 450-acre spread 45 miles northwest of Washington, Renn is totally disillusioned. This summer, he will sell off the last of his herd of heifers. He already has cut back planting to a small vegetable garden in his back yard.

A nearby aluminum factory, an electric power plant and a cement manufacturing company, he said, have fouled the air he and his livestock breathe.

One neighbor after another has sold land for housing subdivisions, and the cow pastures and corn fields slowly are being supplanted by suburban-style bungalows.

"Every new house they build in Frederick County makes it a less desirable place to live," he said. "It is one of the tragedies of agriculture in the county that people have decided there is more money in the sale of land than there is in farming it."

As a protest against continued growth in the county, Renn has given the Maryland Environmental Trust an easement on his property to keep it in agricultural use forever.

Renn's complaints are one illustration of an increasingly serious dilemma faced by county officials: As growth continues and the county is drawn more and more into the metropolitan Washington orbit, can Frederick County retain its identity as an agricultural community?

"We do not want to become an asphalt county. We do not want to lose our agricultural character," says Mary G. Williams, president of the board of county commissioners.

"We are becoming a bedroom community, but we want to balance that with some good industrial growth. We would like to be able to give the people who live here a chance to work here. A lot of them now are going down the road and out of the county to work."

The recent inclusion of neighboring Montgomery County in the Washington Standard Metropolitan Statistical Area -- as defined by the federal interagency committee on SMSAs -- brought Frederick County closer to the official Washington orbit.

Within the next two years, Frederick itself is expected to qualify for inclusion in the Washington SMSA by having a minimum of 15 percent of its work force employed in that area. The new designation will qualify Frederick as a metropolitan area for federal grant-giving purposes, and could mean more federal funds for the county.

Board of commissioners president Wiliams believes Frederick County must get a handle on controlling development so that growth -- which is inevitable -- can be balanced.

In the decade between 1970 and 1980, the population increased by nearly 40 percent from 84,927 to an estimated 118,644, the largest increase in the county's history.

Over the next few years, growth is expected to accelerate as more and more people are drawn by the lure of relatively inexpensive housing and a rural life style. County planning director James R. Shaw estimates that 10,000 more housing units are now in some stage of planning, design or construction.

Stretching from the Potomac River on the south to the Pennsylvania border on the north, Frederick County is the largest in Maryland in land area.

The county became home to Massachusetts-born Francis Scott Key, composer of the "Star Spangled Banner," and was a stronghold of both Union and Confederate sympathizers during the Civil War.

In the spring of 1861, the Maryland legislature convened in what was then the town of Frederick to consider an ordinance of secession, but federal authorities intervened. Members of the assembly were arrested on a variety of charges, and the legislature was never able to get together a quorum to act on the ordinance.

Subsequently, on what John Greenleaf Whittier would descirbe as a "cool September morn," a woman named Barbara Frietchie poke her head from a window in the town of Frederick and addressed a column of Confederate soldiers.

"Shoot, if you must, this old gray head but spare your country's flag,' she said," is how Whittier described the scene in his poem.

More than a century later, Frederick County is a study in contrasts. Despite its recent growth, it is very much a rural county. In summer the meadows are still, as Whittier depicted them, "rich with corn."

Eighty percent of the land is zoned for agricultural use, and farming is still the number one industry. Kenneth Wisner, the diary science agent for the agricultural extension service, puts the number of farms in the county at 1,587, of which 525 are dairy farms. Between $80 million and $90 million worth of farm products are sold outside the county each year, says Wisner.

In the more densley populated areas along the border with Montgomery County or near the city of Frederick, it is not unusual to see cattle or sheep grazing next to newly constructed townhouses or garden apartments, or to see horses tethered in the front yards of split-level ranch houses.

It is one of the ironies of Frederick County that although more than 7,300 acres of land have been rezoned from agricultural to commercial or residential uses in the last 20 years, the number of farms is up slightly.

"In some cases our farms are being consolidated and made bigger," says county agent Wisner. "But in others, they are being divided up into farmettes. There's a real good market out there for doctors and lawyers who want to have a little barn, a horse for the kids and a few animals."

With its 40,000 dairy cows -- one for every three residents of the county -- Frederick remains a major supplier of milk for Washington and Balitmore. It also devotes 60,000 acres of land to fresh corn, and has 20,000 beef cattle, 5,000 hogs and several hundred acres of peach and apple orchards.

The county is at the apex of a triangle formed by Routes 270 wedst from Washington and 70 west from Baltimore. Despite soaring prices of gasoline, it becomes more and more of a commuter county.

Interchanges along 70 and 270 are lined with parked cars during the day after commuters meet to car-pool to work outside the county.

In a study of work patterns of Frederick County residents, University of Maryland Professor William Bellows found that in 1979, 43 percent of them worked outside the county. That figure was up from 28 percent in 1970 and 20 percent in 1960.

Neighboring Montgomery County, where nearly 20 percent of the Frederick County work force is employed, has the lion's share of the commuter business. Slightly more than 4 percent work in the District of Columbia.

Inevitably, more commuters means more families and more families means more schools. Unlike Montgomery and Prince George's counties, where declining enrollments have brought about widespread school closings, the schools in Frederick County are filled to overflowing. Fourteen of 39 schools in the county were operating at levels above 100 percent of capacity last year.

To help pay the cost of serving an expanding school population, the county is actively working to expand its industrial base.

Driving south of the city of Frederick towards Buskeystown and Point of Rocks, planning director Shaw pointed out some of the newer arrivals.

On the left as he heads out of town is an English muffin factory and an asphalt roofing products company. A MacDonald's is under construction just past Rte. 70. "Three months ago, that was Bob and Ann's friut stand," observed Shaw.

A new sewage treatment plant with a daily capacity of 2 million gallons is just coming on line, and its current use is slightly more than 100,000 gallons a day, said Shaw. Clearly, the potential for growth -- residential, commerical or industrial -- is substantial.

None of which pleases Austin Renn.

"I don't like it," said Renn. "But I'm not leaving. I'll spend the rest of my life here. The undertaker will decide when I leave. That's always the best way." CAPTION: Pictures 1 and 2, Church steeples are landmarks in city of Frederick; Austin Renn, farmer in the county since 1928. Photos by Vanessa Barnes Hillian -- The Washington Post; Map, no caption, By Dave Cook -- The Washington Post; Pictures 3 and 4, Downtown Frederick still has a country flavor. Photos by Vanessa Barnes Hillian -- The Washington Post