Once a simple way to send messages, postcards have evolved into collectible objects. What makes them worth collecting?

A canceled family vacation or a compromise of grandma's house instead of a crowded amusement park might yield a pout, a couple of eyerolls, or maybe even a few stomps. That’s understandable.

If you’re taking a vacation, why not take along a few pens, a sheet of 56-cent stamps and an address book and send some postcards during your travels? Postcards – like the ones your grandparents gave ...