Most recent immigrant ancestor - Edwin Bishop Dobell. He was born in 1818 in Staplehurst, Kent, England. He married Harriet Luck on Oct 5 1840 in Cincinnati Ohio and died in the early 1900s there. He was a furniture maker and his parents were Joseph Dobell and Mary Ann Bishop.
Edwin and Harriet had a daughter named Sarah Elizabeth who married George Albert Groff. They had a daughter, Edna, who married Willard Clement Cookman. Edna and Willard are my grandfather Donald's parents.
So my 3rd great grandfather is the most recent immigrant that I am aware of.