The souvenir hunter of the 19th century carried a hammer and chisel, not a cash-stuffed fanny pack. Visitors routinely made off with bits of hallowed sites — Plymouth Rock, Mount Vernon, the White House. The souvenir business arose, in part, to prevent such plundering. “Souvenir Nation,” at the Smithsonian Castle, charts this transformation from genteel looting to robust retail category.

Whether you steal them or buy them, souvenirs are defined by their links to persons, places or events. Value can be “in the eye of the beholder,” says curator William Bird; your most-loved memento may not resonate with anyone but you. If you want a curio collection people will care about in 100 years, apply these strategies drawn from the show.

Always Leave a Note: If no one knows your object’s provenance, it’s worthless. This unexciting wooden dish, thanks to the attached note, proved quite the prize: a hunk of landowner David Burnes’ cottage. George Washington and Burnes feuded over his property, which encompassed the land where the White House now stands. In the end, Burnes sold his considerable holdings but kept his cottage. The home was demolished in 1894; its dismantler saved, and labeled, this piece of rafter.

Grab ’n’ Go: When a historic event goes down, rip a page from the Fall of the Berlin Wall playbook and seize a tangible piece of the action. Bird collects items from political conventions, where, if a candidate knocks ’em dead, “people will be taking everything out of the building” — even the confetti. Broward County, Fla., judge Robert Rosenberg saved the magnifying glass above, which he used to examine hanging chads during the 2000 presidential election.

Locks Are Gold (above left): Try for a lock of a famous person’s hair, a souvenir that was popular for centuries. In 1850, a museum worker named John Varden began amassing hair from presidents and “persons of distinction” such as Samuel Morse and Henry Clay. (Their locks, and others’, adorn the plaque above.) “Hair is the ultimate memento,” Bird says. “It’s lived with the person.” How you get this hair, we don’t know. Ask nicely? Promise not to use it for cloning?

When in Doubt, Don’t Throw It Out (above right): If an object is designed to be a keepsake, KEEP IT, especially if it commemorates a first or an anniversary. Such limited-edition pieces have longevity. The jail-door pin at right was awarded to suffragettes who did time for picketing the White House in 1917. It was treasured then as a badge of honor, and is today for its rarity and beauty as well.

The Book

William Bird’s “Souvenir Nation” companion book plumbs the psychology behind our yen to collect. And it showcases nifty items not in the exhibit, like the chairs from the legendary Sept. 26, 1960, Kennedy-Nixon throwdown, the first presidential debate to be televised.

Evolution of a Souvenir

These items from Mount Vernon trace the path of souvenirs from highly personal keepsakes to random crap.

Piece of George Washington’s coffin (circa 1840): George got a new tomb and a new coffin in 1837. Bits of the old coffin were distributed to VIPs like Leverett Saltonstall, the Massachusetts congressman and family friend who owned the chunk pictured here.

Ivy from Mount Vernon grounds (1879): As Mount Vernon grew more touristy, the management started selling pieces of the estate’s plant life — like this piece of ivy wood — to keep visitors from stealing.

Miniature compass (circa 1910): This little guy, meant to be worn as a charm, combines a morsel of the real thing — a buckeye from a Mount Vernon tree — with a non-local component, the compass.

George Washington’s dentures magnet (2013): Mass-produced tchotchkes like this $6.95 magnet are now standard fare at Mount Vernon’s gift shop.

Smithsonian Castle, 1000 Jefferson Drive SW; 8:30 a.m.–5:30 p.m. daily, through August 2014, free; 202-633-1000, (Smithsonian)