MONTICELLO: (monticello.org) Thomas Jefferson’s 5,000-acre plantation in Charlottesville, Va., is a monument to one of America’s greatest thinkers. Among his extraordinary accomplishments: penning the Declaration of Independence, serving two terms as president and founding the University of Virginia. Visit his house and stroll the gardens where he experimented with more than 250 varieties of fruits and vegetables. Even jaded teens will love hearing that recent DNA evidence strongly suggests Jefferson fathered several children with one of his slaves. Adults: $13. Children 6 to 11: $6. Stay at the Clifton Inn, a 1799 country estate once owned by Jefferson’s son-in-law. (See cliftoninn.com for rates starting at $165.)

LIBRARY OF CONGRESS: (loc.gov) The world’s largest library isn’t just a pile of books. Among the 121 million items in its collection: the eyeglasses and Confederate money that were in Abraham Lincoln’s pocket the night he was shot, and George Gershwin’s handwritten lyrics for “God Bless America.” Admission is free. Stay at the Morrison House, a Colonial-style manor house in nearby Alexandria, Va. (Go to morrisonhouse.com for rates from $200.)

UNDERGROUND RAILROAD: (undergroundrailroad.org) As many as 100,000 escaped slaves traveled along a trail of paths, creeks, swamps and safe houses on their run to freedom in the Northern states and Canada, helped mainly by Quakers and freed slaves. Find a site on the Web, or plan a trip to the Levi Coffin house in Fountain City, Ind., where hundreds of fleeing slaves hid from bounty hunters. Adults: $2. Children over 6: $1. Stay at the Phillip W. Smith House, a bed-and-breakfast in an 1890 inn. (Go to pwsmithbnb.com for rates starting at $79.)

LEWIS AND CLARK EXPEDITION: (nps.gov/lecl) It’s the bicentennial of the duo’s 28-month-long trek across the uncharted Western territory. Find a site along the route online, or plan a trip to the Lewis and Clark National Historic Trail Interpretive Center in Great Falls, Mont., near where the explorers and their entourage (including –Sacagawea and her baby) spent a month figuring out how to get around the gigantic falls. This summer, you can take a guided hike along the Missouri River to an encampment of re-enactors. Adults: $5. Children 6 to 17: $2. Stay at the Charlie Russell Manor, a Georgian-style mansion. (Try charlie-russell.com for rates starting at $95.)

KITTY HAWK, N.C.: (nps.gov/wrbr) Time flies; it’s been 100 years since Wilbur and Orville Wright’s first takeoff from atop a large sand dune called Kill Devil Hill. (Kitty Hawk, four miles down the coast, grabbed the glory because it had the nearest telegraph.) For a refresher course on American ingenuity, check out the visitors center, which houses a replica of the original flier. Adults: $3. Kids under 16: free. Stay at a nearby summer cottage instead of a hotel (outerbanks.com).