MAINE: Acadia National Park
Rangers offer kids' programs on the rocky coastline, or families can drive to scenic Cadillac Mountain. (For info on visitors' centers in three locations, go to www.nps.gov/acad.)
MARYLAND: Fort McHenry
See the flag raised over the fort that inspired Francis Scott Key to write "The Star Spangled Banner" during the Battle of Baltimore, and visit the barracks and guardhouse.
MASSACHUSETTS: Freedom Trail
Follow a painted line on the street as you walk the 2.5 miles from Boston Common past the Old North Church and site of the Boston massacre to Faneuil Hall.
MICHIGAN: Henry Ford Museum
Ford's Dearborn complex -- called the largest indoor-outdoor museum in the nation -- includes a re-created village with houses, farms, and shops, plus an IMAX Theatre.
MINNESOTA: Minnehaha Park and Falls
During a visit to Minneapolis, take in the 53-foot waterfall immortalized by Henry Wadsworth Longfellow in his Song of Hiawatha, and stay to bike and picnic.
MISSISSIPPI: Vicksburg National Military Park
Site of one of the Civil War's most important battles, the park includes 144 cannons and some 1,000 monuments and markers.
MISSOURI: Gateway Arch
Ascend to the top via tram, visit the Museum of Westward Expansion, or take a riverboat cruise at this family-friendly St. Louis attraction.
MONTANA: Little Bighorn Battlefield
Site of Custer's Last Stand, this park includes a museum of artifacts from the battle and the Custer National Cemetery.
NEBRASKA: Chimney Rock
Snap your picture at this famed rock formation in Bayard, a landmark in the westward expansion on the Oregon Trail.
NEVADA: Hoover Dam
Built in 1935 near Boulder City, this awesome engineering marvel spans the Colorado River and includes a film on the dam's construction and history and an observation deck.
NEW HAMPSHIRE: Mount Washington
Ascend to the observatory at the top of the highest mountain in the Northeast via the Mount Washington Cog Railway, which makes the picturesque climb at a steep tilt.
NEW JERSEY: Cape May Lighthouse
After riding a trolley through Cape May's historic district, you can make the 218-step climb to the top of its landmark lighthouse.
NEW MEXICO: Carlsbad Caverns
This huge site houses the world's largest network of caves; most visitors focus on the Big Room's surreal formations and eerie glow.
NEW YORK: Ellis Island
Kids can look for their ancestors at this restored immigration museum in New York Harbor, where more than 12 million people entered the U.S. in search of opportunity and freedom.
NORTH CAROLINA: Wright Brothers Memorial
Explore aeronautic memorabilia and climb Kill Devil Hill for a look at the 60-foot monument commemorating the Wrights' first flight in 1903.
NORTH DAKOTA: Frontier Village
The big draw -- and we mean big -- is the statue of a buffalo that dominates this re-created Wild West town in Jamestown, complete with jail, schoolhouse, and railway station.
OHIO: Underground Railroad & Freedom Center
This $110 million facility, set to open this summer in Cincinnati, honors the legacy of the Underground Railroad.
OKLAHOMA: Robbers Cave
Discover why Jesse James, Belle Starr, and Cole Younger used this Wilburton cave as their hideout, then canoe and ride horses nearby.
OREGON: Mount Hood Railroad
Rail buffs of all ages can enjoy the scenery at the base of Mount Hood aboard historic trains, with a stopover in pretty Parkdale.
PENNSYLVANIA: Liberty Bell
In its new location in Philadelphia's Liberty Bell Center, this symbol of freedom and nearby Independence Hall are must-sees.