Inbreeding of the Lewis rat is begun by Dr. Margaret Lewis from a Wistar stock. In 1924, at F20 to Aptekman and Bogdon. In 1958, at F31 to Silvers, who distributed this strain subsequently.
To Central Institute for Laboratory Animal Breeding, Hannover, in 1973 at F58. In 1994, to Harlan Netherlands through acquisition of Central Institute for Laboratory Animal Breeding. Harlan became Envigo on 2015.