Bird is a curator at the Smithsonian Institution's National Museum of American History and the author of "Souvenir Nation," a book coming out May 21 that explores the origins of 50 of the museum's most interesting relics originally saved as keepsakes.

What in your museum work gave you the idea to write this book?

I curate one of the oldest collections in the museum. As the museum grew, the collection was divided up. But every time a division was made, things that didn't quite fit the new way of thinking about the museum were left behind. So we have this reliquary of unclaimed and not taken objects. The more I looked at these things, I noticed that they shared certain characteristics. Most are pieces of larger things that people took when they traveled or were given. And so it suggested to me that these were actually souvenirs. It's something that's so fundamental and elemental to any museum. Before you can have a museum, you need people who save things.

What sets these objects apart from the rest of the items in the museum?

They're small, they're personal, they're the kind of thing you could fit in a pocket or a purse. And they're all pretty nondescript -- they're rocks, they're bits of wood. They probably would have been thrown away long ago. In the past, they've been presented as kind of a one-off -- a piece of Plymouth Rock, a fragment of Mount Vernon. If you look at them as a group, they teach lessons about how people once thought they could save the past. There's something kind of charming about it.

Are we still a souvenir nation?

Absolutely. It's never really stopped. You can still find people for whom even the smallest thing is so personal that the museum can't collect it. It means so much to them. It's still going on.

- Matt Connolly