Did Deserts Cover Much of North America 10,000–100,000 Years Ago?

No. Between 10,000 and 100,000 years ago—spanning the last glacial period (Wisconsin glaciation) and the preceding interglacial—North America was generally wetter and cooler than today. Vast ice sheets covered Canada and the northern U.S., while the southwestern deserts were smaller and less arid. Pluvial lakes (like Lake Bonneville and Lake Lahontan) filled basins now occupied by salt flats. Grasslands and woodlands extended farther south. True desert conditions expanded significantly only after the Holocene warming began around 11,700 years ago.