Washington Dulles International

The companion to the Smithsonian's National Air and Space Museum on the Mall — and the place they put the artifacts too big for downtown. Opened in 2003 in a vast 760,000-square-foot hangar on the south side of Dulles, it holds around 200 aircraft and spacecraft and 3,000 artifacts, and the roll call is staggering: the Space Shuttle Discovery, the most-flown orbiter in history, with its re-entry scars still on the tiles; the Enola Gay; an SR-71 Blackbird; a Concorde; and the Boeing 367-80, the prototype that became the 707 and the jet age. The Donald D. Engen Observation Tower overlooks the Dulles runways — one of the best legal spots in the country to watch heavy iron work while standing next to a spaceship. Admission is free.

George Washington's plantation home sits on a bluff above the Potomac eight miles south of Alexandria, the house he expanded over decades into the red-roofed mansion with its iconic two-story piazza facing the river — a porch he designed himself, where he liked to sit and watch the water. He was born into it, inherited it, farmed it as an experimental agriculturalist, returned to it after the Revolution and again after the presidency, and is buried in the tomb on the grounds with Martha. Like Monticello, the modern estate interprets the full story, including the more than 300 enslaved people who ran the plantation. Saved from ruin in the 1850s by the Mount Vernon Ladies' Association — the first national historic-preservation group in America — it has been open to the public ever since.

Harpers Ferry sits on a spit of land where the Potomac and Shenandoah rivers join and three states — West Virginia, Maryland, and Virginia — come together, walled in by steep wooded heights. Thomas Jefferson stood here in 1783 and called the view "worth a voyage across the Atlantic." Its position made it a natural arsenal town, and in October 1859 the abolitionist John Brown seized the federal armory here in a raid meant to spark a slave uprising; he was captured (by US Marines under Robert E. Lee) and hanged, but the raid lit the fuse of the Civil War. The town changed hands a reported eight times during the war. Today the lower town is preserved as a national historical park, the Appalachian Trail Conservancy headquarters sits here at the trail's symbolic midpoint, and the rivers and railroad still define the gap.

Three miles south of Sharpsburg, Maryland — the site of the September 17, 1862 Battle of Antietam, the single bloodiest day in American military history. 22,717 Union and Confederate soldiers were killed, wounded, or missing in twelve hours of fighting along Antietam Creek and the cornfields, sunken road ("Bloody Lane"), and stone bridge ("Burnside Bridge") that anchor today's preserved battlefield. The tactical result was a draw, but the strategic result was Robert E. Lee's first invasion of the North turned back — which gave President Lincoln the political cover to issue the preliminary Emancipation Proclamation five days later, on September 22, 1862, transforming the Civil War from a war to preserve the Union into a war to end slavery. The battlefield preserves 3,250 acres and most major terrain features look essentially as they did in 1862 — the Dunker Church (the photograph reference point for one of the most-published images of the Civil War), the cornfield, the sunken road, Burnside Bridge over Antietam Creek. The National Cemetery on the hill holds 4,776 Union dead. Photographer Alexander Gardner's images of the battlefield dead, displayed at Mathew Brady's New York studio in October 1862, were the first time the American public saw the dead of war — and arguably the moment war photography was invented.