Nevada contains the largest desert area in the United States. The Great Basin Desert—the largest desert entirely within the contiguous U.S.—covers most of Nevada plus portions of Oregon, Idaho, and Utah.
Nevada also includes portions of the Mojave Desert (southern tip, including Las Vegas area) and transition zones to the Sonoran Desert. This makes Nevada the most desert-dominated state by land area percentage.
California has larger total desert area (Mojave + Colorado/Sonoran) but Nevada has the highest proportion of desert land.