A stand of chestnut oaks stirs in the summer breeze, leaves gleaming in the bright sun. The grass at their feet is unmowed and unraked, preserved just as it was, and they are protected by an old iron fence because they are all that is left of the Clump of Trees.

Exactly 120 years ago this weekend Robert E. Lee sent 13,000 men to take that clump of trees, much broader then, with a tall umbrella-shaped one in the middle. He ordered George Pickett's brigades to march straight for it, the units on the right angling in to focus on the point like rays to a burning glass. It was the heart of the Union line at Gettysburg, almost a mile away across rising open fields, and the Rebels came on in three grand lines two miles from end to end, a heart-stopping sight that brought a hush over the entire battlefield.

Pickett's charge bled to death on those broad meadows as 7,000 men fell under artillery crossfire and canister at point blank and the long line of Union rifles. Barely 200 men got all the way to the little jog in the low stone wall next to the trees, to be immediately killed or captured. Historians like to say that this jog in the wall, the Angle, was the high-water mark of the battle, the war and the Confederacy itself.

Along here, the grass is neatly cropped. A line of cannon looks out over the wall and the undulant, slightly sloping ground. A crew of painters in yellow hard hats is touching up the cannon, and tourists watch them. All day long a stream of cars passes by here, following the auto-tour map, and the people stop, and some get out to read the inscriptions on the iron tablets and gaze across the meadow to its far edge, where the attack began, and beyond to the blue mountains from which Lee's army came and to which it returned.

It is a lovely day, hot and clear, with cotton clouds and the sound of crickets and the smell of mown hay and clover and honeysuckle. Down the slope, cows graze belly-deep in thick grass. Granite knuckles jut up through the soil, spotted with lichen like the back of an old hand. There is a lot of granite at Gettysburg. The bullets whined as they caromed off it.

The tour does not follow the logic of the three-day battle but goes backward, from Pickett's charge on July 3 to the fight for Little Round Top on the Union left flank the day before. A sign directs you to the place where the 20th Maine under Col. Joshua Lawrence Chamberlain held the extreme end, on the far side of the hill among the trees and boulders. Out of ammunition, exhausted after beating back enemy rushes for hours, about to be overwhelmed, Chamberlain ordered . . . a bayonet charge. It turned the whole line.

You can see the modest monument, the big rock where he anchored his regiment, the elegant New England stone wall his men built in the dark that night. The wall is 100 yards long. All over the woods, even behind boulders and down ravines, monuments have been placed by the various units that fought there, but none is as eloquent as that wall.

Gettysburg, in fact, has monuments like a barn has mice. They stand along the highways and side roads, with cannon sprinkled among them. They rear up in the middle of cornfields. They loom, horrendous Victorian pomposities in the form of Greek temples, Roman pantheons and Palladian villas, on every knoll and dip, by every curve in the road, clustering hugely wherever the action was hottest. Topped by horsemen, riflemen, dying soldiers, victory angels, flag wavers, cannonballs, eagles, forage caps or crossed bayonets, faced with laconic tablets that give the accounting in dead and wounded, they commemorate practically every brigade that fought here.

They are irritating at first. After a while they get to you in their homeliness, the sheer numbers of them. You see a stone marker in someone's back yard, and you remember what a small-town war it was, with its Wheatfields and Peach Orchards and Farmhouses, its suddenly-famous hills and springs and woods and turnpikes, homespun landmarks of a nation of farmers.

There seem to be more Union monuments than Confederate. Maybe that is because there were 95,000 in the Army of the Potomac here, 35,000 of them Pennsylvanians fighting on home ground (including Wesley Culp, who moved south before the war, joined the Confederates and marched north to die on his father's farm, right outside of town on Culp's Hill), and only 73,000 from the Army of Northern Virginia. And the Union did win, after all, at a cost of 23,045 casualties. The South lost 20,688.

With the tour, the electric map at the visitor center, the wonderful 356-foot-around cyclorama painting of the battle's climax, and a climb up the once-controversial 393-foot National Tower, you come to understand or at least to sense what happened here, and why, and the might-have-beens, and the terrible uproar and smoke and dust and blood, and the pity of it all.

It was a battle that invented itself, starting just after 5 a.m. on July 1, 1863, a Wednesday. Confederate advance forces, probing blindly eastward from Chambersburg--J.E.B. Stuart and his cavalry, the vital antennae of the army, were gone glory riding somewhere--ran into John Buford's cavalry, and a skirmish started.

Buford, a man ahead of his time, saw cavalry not as dashing caped swordsmen but as mobilized infantry. His people fought dismounted, with the new repeating carbines instead of standard-issue muzzleloaders, and now they held the powerful Rebel assaults, keeping the enemy from reaching the ridges and knolls embracing the small town of Gettysburg. Increasingly outnumbered, Buford hung on for five hours while units of both armies raced to the scene and a full-scale battle developed.

Had he not held them off, the Confederates would have occupied the ridges, and the battle, if there had been one at all, would have happened somewhere else, perhaps on the other side of that same ridge, with the Rebels hunkered down behind the rocks and the Yankees charging uphill across the fields . . .

As it was, Confederates flanked them on the north, overran the village and had a chance to sweep clean over the ridge and Culp's Hill and win it right there. But they didn't, and the first day ended with soldiers still pouring into town from all directions.

On July 2, Lee tried the Union left, where Daniel Sickles had advanced down off the ridge without orders, to leave the whole flank dangling in the air. After hours of delay, James Longstreet came at him through the Peach Orchard and Wheatfield and a monstrous jumble of boulders called Devil's Den, on up to Little Round Top. This attack failed, too, as did an all-out lunge for Culp's Hill on the other end.

Finally, on the third day, Lee went for the Union center. That was Pickett's charge.

"I alone am to blame," Lee said afterward.

If the cavalier Stuart had caused the battle in the first place, by not being there to do his job, it was Lee, the other great cavalier, who lost it because he had not yet learned that courage is not enough. (Longstreet, designer of trenches, understood the meaning of bloody Fredericksburg six months earlier: No matter how brave you are, you can't take a fortified position by running at it across open fields. But he was two wars ahead of conventional military thinking. They were still doing it in 1916.)

At the time of the battle, Gettysburg was a village of whitewashed carpenter-gothic houses, population 2,000. The local paper, the Star and Banner, noted on July 2 that "the rebels were encamped in large force above Cashtown on Monday night. On Tuesday morning they advanced to within a half mile of Gettysburg . . . but on the advance of the Union army, they pulled up stakes and skedaddled."

That issue didn't come out until July 9, when it was combined with the post-battle issue. The lead editorial ("Just as we were ready to go to press on Wednesday the most terrific battle of the war commenced . . .") is mainly concerned that the Southern invaders had used the presses and pied the type. A long account of the battle, the biggest story the paper ever had dropped in its lap, is reprinted from the New York Times, but some local details are added:

"Persons visiting the battlefield should be careful in handling the shells and guns strewn over the ground . . . Men, Horses and Wagons wanted immediately, to bury the dead and to cleanse our streets . . .

"The saddest incident connected with the battle at this place was the killing of Miss Mary Virginia Wade, by the rebel sharpshooters posted in the outskirts of the town. She was attending a sick sister at the time, and the house standing in an exposed position, she was in constant danger. A minie ball from one of their rifles struck her in the head and killed her instantly. Miss Wade was aged 20 years, 1 month and 7 days, and was a young lady of good character and much respected . . ."

(Jennie Wade was engaged to Cpl. Johnston Skelly, who had been wounded in the battle of Winchester two weeks earlier and died in Confederate hands. The story was that he had whispered his last words to a Rebel soldier who said he came from Gettysburg and would give her the message if he ever got there. He was Pvt. Wesley Culp.)

Today, downtown Gettysburg has definitely got over the shock of being the site of a major event. The battle is a local industry. The billboards begin 18 miles out of town. There is a Battle Theater and Cafeteria, a Civil War Art Gallery, a wax museum, Mister Ed's Battlefield Tape Tours and other tours by bus, private car, foot, bicycle and helicopter. There are also spinoffs ranging from the Lincoln Train and the Eisenhower Farm to the Reliance Mine Saloon and the Land of Little Horses.

Chain hotels, chain restaurants, an air-conditioned tower with two elevators: big-city techniques for remembering a small-town war. But for all the hucksters and monuments and the 30 miles of special roads, for all the rows and rows of weathered stone names in the cemetery, Gettysburg remains very close, very personal. "In Memoriam of our comrades, 75th Pa. Vols." says a sign, its Latin fanciness somehow touching because it is trying to say more than it can.

This is one tourist attraction you can't just drive through. You have to get out and smell the sweet air and feel the summer heat on your back and hear the granite rubble crunch underfoot, because then you remember that it is hallowed ground, as the man said, but also, more simply, it is a place in Pennsylvania where thousands of Americans, drawn together by circumstance, remained to create history for three days in July, 120 years ago. Something of them is still here.