I think the most famous work of Don Rosa is the series whose English title (I think) is "The life and times of Scrooge McDucky" which tells about the youth and the whole life of Scrooge McDuck beginning in the 1870s. As a historian one cannot but love those comics as Don Rosa let so many historical events and characters (among many others Teddy Roosevelt, Wyatt Earp, Jesse James, Geronimo, Czar Nicholas II. appear).
Also Don Rosa's comics are full of references to the earlier comics by Carl Barks.