Yellowstone’s summer climate is invigorating and delightful. Frequent, but fleeting, rainstorms tend to modify the prevailing atmospheric aridity. Evenings and nights are invariably cool. The highest temperature ever recorded at Mammoth was 92.4°, while the lowest on record was 66° below zero. This record low was taken at Riverside Station near West Gate on February 9, 1933.[10] Such is the physical setting of this mountainous country. Its western slope was called the land of “Ee-dah-how.” This was a Shoshone exclamation that means “Behold! the sun is streaming down from the mountain tops; it is sunup, time to get up!”[11] It is expedient that a brief review of early American history should be given as a setting for the major interests in the drama of Yellowstone. The history of Wonderland falls logically into three periods: Archaeological characteristics and association; Modern discovery and exploration; Development as a pleasuring ground by the United States Government. The greater part of the Yellowstone area was a part of the Louisiana Purchase, whereas that portion under the Snake River drainage appertained to the great Pacific Northwest. All of the territory involved once belonged to Spain. However, the Spanish claim was relinquished in a series of treaties beginning with San Ildefonso in 1800, wherein the province of Louisiana was retroceded to France under the dictation of Napoleon Bonaparte. The balance of Spanish interests above the forty-second parallel was extinguished in favor of the United States in 1819.