C

• [+] Colorado Plateau (0)

D

• [+] Mojave Desert (8)
• [+] Sonoran Desert (8)

G

• [+] Grand Canyon (4)
• [+] Great Basin (13)

P

• [+] Pacific Northwest (7)

R

• [+] Rio Grande (2)

R cont.

• [+] Rocky Mountains (2)

S

• [+] Sierra Nevada (5)
• [+] Southwestern United States (9)

Y

• [+] Yellowstone (2)

C

• Cross Timbers

G

• Great Basin
• Great Plains

H

• High Plains (United States)

I

• Intermountain West

J

• Jell-O Belt

L

• Llano Estacado

M

• Mormon Corridor
• Mountain States

N

• Northwestern United States

O

• Ogallala Aquifer
• Osage Plains

P

• Prairie Pothole Region

S

• Southwestern United States