Where in the U.S. can I go to see fireflies?

Growing up in Costa Rica, I remember catching fireflies in my hand as a child, and the wonder at seeing them on a summer night.

My wife has never seen a firefly. I would like to know if there is a place in the U.S. where there are fireflies. I don’t think we have them in the S. F. Bay Area, but then again, I haven’t gone out into the woods at night to search for them. In Costa Rica, we had them in our backyards.