I found some old 1900 census records from the Grand Ronde Indian Reservation and found some information regarding the Riggs family:
Solomon Riggs, born in 1830 in Oregon is listed as 100% Umpqua Indian. His wife, Jane Riggs, born in Oregon in 1848 is listed as 1/2 Umatilla Indian (on her mother's side) and white on her father's side.
Together, they had the following children: Willie (1884) Andrew (1881) Sammy (1887) Lewis (1893)
There is also a grandchild of Solomon in the home named Joseph Sulky (born in Oregon in 1889. Joseph is listed as Yamhill Indian on his father's side and Umatilla Indian on his mother's side.
There is an adjacent household with a man named Edward Riggs (born in Oregon in 1874) who is 100% Umpqua Indian. His wife, Alice Riggs (born in Oregon in 1870), is listed as Shasta Indian on her father's side and Rogue River Indian on her mother's side.
I hope this helps someone connect to their Native heritage!