My information on the Lewis side is pretty sketchy.
Augustus was born in New York in 1820. His father was born in Pennsylvania, his mother in NY. He was in Wisconsin in 1850-1880 and moved to California for a few years. His sons Frank, Bert, and Dwight spent their lives in the San Francisco Bay Area. His other children remained in Wisconsin. He returned to Wisconsin after the death of his wife, Mary, and died there in 1908.
Mary was born Mary Legross, in Rodman, Jefferson Cty, NY. Her parents were Phebe Wright and Daniel Legross. Phebe was born in New Hampshire. I don't know anything about her family.
Daniel Legross was the son of Francis Legross and Dorothy Barker. Francis was born on the Isle of Jersey and Dorothy's line traces back in Massachusetts to the early 1600's.
In short, I don't know about a Native American branch or an adopted daughter.