text: A smallpox epidemic broke out in Mexico City in 1779/1780. It slowly spread northward through the Spanish empire, by trade and warfare, reaching the northern plains in 1781. The Comanche and Shoshone had become infected and carried the disease throughout their territory. Other warring and trading peoples also became infected. The Mandan lost so many people that the number of clans was reduced from thirteen to seven; three clan names from villages west of the Missouri were lost altogether. They eventually moved northward about 25 miles, and consolidated into two villages, one on each side of the river, as they rebuilt following the epidemic. Similarly afflicted, the much reduced Hidatsa people joined them for defense. Through and after the epidemic, they were raided by Lakota Sioux and Crow warriors.
  In 1796 the Mandan were visited by the Welsh explorer John Evans, who was hoping to find proof that their language contained Welsh words. Numerous European Americans held that there were Welsh Indians in these remote areas, a persistent myth that was widely written about. Evans had arrived in St. Louis two years prior, and after being imprisoned for a year, was hired by Spanish authorities to lead an expedition to chart the upper Missouri. Evans spent the winter of 1796–97 with the Mandan but found no evidence of any Welsh influence. In July 1797 he wrote to Dr. Samuel Jones, "Thus having explored and charted the Missurie for 1,800 miles and by my Communications with the Indians this side of the Pacific Ocean from 35 to 49 degrees of Latitude, I am able to inform you that there is no such People as the Welsh Indians."