I have been gardening for black swallowtail butterflies for several years now.  It's amazing to watch the lifecycle, or metamorphosis, of butterflies in your own backyard.

Butterflies feed on the nectar from flowers.  Plant flowers full of nectar to attract them.  Some top  choices would be cosmos, butterfly bush, zinnia, joe-pye weed, pentas, lantana, purple coneflower, salvia, yarrow, firebush, blazing star, and mexican sunflowers.