Lewis and Clark

Today, in 1806, Lewis and Clark returned to St. Louis after spending over two years exploring the headwaters of the Missouri River in an effort to find a route to the Pacific. 

They returned with their journals and with plant specimens. Here's just a handful of the plants they discovered (I picked the ones you might be the most familiar with):
Snow-on-the-mountain (Euphorbia marginata)
Creeping juniper (Juniperus horizontalis)
False indigo (Amorpha fruticosa)
Needle-and-thread grass also called porcupine grass (Hesperostipa comata)
Purple coneflower (Echinacea angustifolia)
Rough gayfeather also called large button snakeroot (Liatris aspera)
Wild four-o'clock (Mirabilis nyctaginea)
Wild rice (Zizania palustris)
Wild rose (Rosa arkansana)