Close-up of "snowballs" of borax created as spring rains and runoff evaporate from the valley floor forming large alkalia flats. The first form of borax to be found in the Valley was white crystalline ulexite called “cottonball”, which encrusted the ancient lake bed, Lake Manly. Death Valley National Monument Est. February 11, 1933; Death Valley National Park in 1994. 5,270 square miles (13,649 km2). Inyo County, CA.