Many Americans in the early 1800s believed the Mandan Indians were descended from Welsh explorers led by Prince Madoc around 1170 AD, as so many of them were so light skinned.
Barry Fell ping
I've read that Thomas Jefferson told Lewis and Clark to not mention any Welsh speaking, light skinned Indians in their report. His fear was that some European power may use that fact as an excuse to claim western portions of what would eventually become the USA. So...the official position of the US government was/is to deny anything Welsh in early America.
We used to have a bronze plaque at Ft Morgan that commerated Prince Madoc's arrival in America in 1170 AD. It was blown down in hurricane Fredric in 1979. It was put into storage and never re-installed.
Alabama Fights To Reinstate Plaque Celebrating Welsh Columbus
Local Legend Says Prince Madoc of Wales Discovered America In The Year 1170.
"Were There Welshmen on the Shores of Mobile Bay 300 Years Before Columbus "Discovered" America?"