MONTPELIER, the gorgeous central Virginia estate of President James Madison, has always been overshadowed by Thomas Jefferson's Monticello, just as the reputation of "the great little Madison" has lagged behind Long Tom's.

This is partly because Montpelier is somewhat off the beaten track but mainly because hardly anyone in living memory has been allowed to see the place. From the turn of the century until last fall, the estate was held by descendants of E.I. du Pont, the gunpowder king who founded one of America's richest families.

The public was admitted only on the first Saturday in November, and then only as far as the lower lawn, from which the unwashed could watch the Montpelier Races, a principal event of the Old Dominion's horsey set. Otherwise Marion du Pont Scott, who inherited the place in 1926, lived there in quiet and rather eccentric splendor until her death, at 89, in 1983. (Although she was married to actor Randolph Scott only from 1936 to 1938, she kept the name for the rest of her life.)

Now Montpelier, 85 miles from Washington, is open to the public every Saturday, and we get to see a lot more than just the lawn. After a year-long squabble over Scott's will, the 2,700-acre estate was sold to the National Trust for Historic Preservation as a shrine to our fourth president (with, by stipulation, two rooms dedicated to Scott's father, William du Pont, who bought the place in 1900).

"I wish we could be open every day, and I'm sorry the mansion itself will have to remain closed for the time being," says estate director George Smith. "There is a very great deal of work to be done before we can get into a full-scale tour operation."

Tours are guided by docents and limited to areas around the main house and gardens, because much of the rest of the estate is being leased by a race horse owner and trainer.

The National Trust is a nonprofit organization, and Montpelier certainly seems unlikely to change that: One member of the du Pont family said it takes at least $120,000 a year just to minimally maintain the vast main house (52 rooms, 12 baths), the 42 tenant dwellings, the 30 barns (with stalls for 175 horses) and sheds, the 10,000-square-foot greenhouse, the 10 miles of paved roads (with seven bridges), the two-acre walled formal garden, the schoolhouse, the Olympic-size swimming pool, the steam laundry, the bowling alley, the sawmill, the private Norfolk Southern railroad station and siding . . . .

Hardly any of the above has anything to do with James and/or Dolley Madison, of course, and the National Trust's interpreters are likely to have a tough time keeping a visitor's attention focused on the Founding Father. The formal garden, a number of exotic trees, and some sections of the central part of the mansion are about all thmains of the Madisons' handiwork. Everybody's favorite is a massive cedar of Lebanon, which Montpelier landscape superintendent Mark Nilsson says "is certainly of Madison's time and, according to tradition, was planted by his own hand."

Nilsson bounds around the estate as happily as a rabbit in clover, finding floral marvels on every hand. No fewer than 75 varieties of daylilies have been catalogued, for instance, and the hundreds of acres of woodlands are a wildflower riot in spring.

The mansion is not easily described. "Well, it's rather a hodgepodge," Smith says. "Sort of a modified Catskills hotel with Palladian and art deco features." The estate passed through more than a dozen owners between Dolley Madison and William du Pont, and some of them made major alterations. During their 83 years of occupancy, the du Ponts left hardly a stone unturned, so meticulous measured drawings must be made before anyone can do much more than guess at what's original.

The submergence of the Madison masonry parallels that of his reputation. As Madison left office in 1817, John Adams said of him that, "Notwithstanding a thousand faults and blunders, his administration has acquired more glory, and established more Union, than all his three Predecessors, Washington, Adams and Jefferson, put together."

This generous assessment is shared by some historians, but even the dramatics of the War of 1812 didn't help fix Madison in our memory. We all know how he and Dolley fled just before the British burned the White House, but who remembers that Madison was the only serving chief executive to command troops in battle (at Bladensburg, when he took over for their fallen commander).

Madison had an abiding passion for science, which he applied so skillfully in his management of Montpelier's grounds and garden that Jefferson called him "the best farmer in the world." Madison made his plantation pay while neighbor Jefferson's was going broke, yet who do we celebrate as our Great Gardener?

Jefferson is called the founder of the University of Virginia -- indeed, he had it carved on his tombstone -- but it was Madison, more than anyone else, who over many years helped him mature the plans for the "academical village." Madison was a charter member of the board of visitors, a hardworking fundraiser for the school, and lobbied the state legislature on its behalf. When Jefferson died, Madison became rector of the university and devoted much of his last decade to institutionalizing Jefferson's dream; he is largely responsible for the fact that it endured. You could spend a lot of time in Charlottesville without anybody telling you any of this.

The opening of Montpelier to the public may spark a revival of interest in Madison, suffer though he may from having been so "abnormally normal," as one researcher put it. In any case it's a major addition to Virginia's tourist attractions even though visitors may only peek in the windows of the mansion.

While restoration and excavation will be necessary to highlight the Madison elements that remain, the estate as it stands is a wonderful study in the ways of the wealthy. At its height during the du Pont era, Montpelier was an all but self-sufficient village, with its own power plant and a private police force that kept the place private. Cockfighting, for instance, has been illegal in Virginia since the mind of man runneth not to the contrary, but Montpelier has quite a fancy cockpit, and it hasn't been that long since it was in regular use.

There are wonderful cross-connections in the family histories of the Madisons and du Ponts. E.I. du Pont's French father corresponded with Madison when he was secretary of state; according to published accounts, John Tayloe, owner of Washington's Octagon House, where James and Dolley Madison moved after the British burned them out of the executive mansion, was a great-great- grandfather of Randolph Scott; and one of Randolph Scott's great-great-grandmothers is said to have been a sister of Dolley Madison. (George) Randolph Scott, now 87, is an Orange County native who lives in Beverly Hills, where he manages a fortune said to exceed that of his former wife.

Their divorce was quite amicable. Scott had gone to the west for his health; one day he ran into Howard Hughes on a golf course and Hughes gave him a part in a western. Eventually Scott made more than a hundred of them. Meanwhile, back at the ranch, Marion Scott was overseeing an increasingly famous and successful stud farm, which reached its zenith when her stallion Battleship, a son of Man O War, won the Grand National at Aintree, England, in 1938, a triumph more or less equivalent to those bloody Australians carrying off the America's Cup.

"It's merely a case of being separated too much, which did not prove compatible with marriage," Virginia gentleman Scott said of the reason for the divorce. They remained very close friends, and the actor was a regular visitor to Montpelier.

Marion Scott was by all accounts an autocrat of the first water, yet her former associates and employees speak of her, when they can be brought to discuss her with strangers at all, with a good deal of respect and even some affection. Those who served her faithfully sometimes were given free land (on the other side of the tracks from Montpelier) and free loans to build homes.

As her age increased and her eyesight diminished, her driving became increasingly erratic, so that it became even-odds on any given morning whether she'd make it to the stables, which she visited every day.

Hauling her car off of fences and out of ditches was a regular chore -- and an odious one on the day she pranged a manure wagon -- but after she nearly wiped out one of the estate workers it became obvious that something had to be done.

Did they take her keys away? Jamais la vie! They put a revolving red light on top of her car, wired to flash and whirl whenever the engine was running, to warn everyone to watch out, here she came.

MONTPELIER ESTATE -- Open Saturdays 9 to 4. Admission $3 adults, $1.50 students (first through 12th grades), $2.50 seniors.

GETTING THERE -- I-66 south to U.S. 29 south to U.S. 15 south; in Orange, turn west on Virginia Rte. 20 four miles to Montpelier Station.