In 1921, Little used a mouse strain of Abby Lathrop, and female 57 was mated with male 52 to obtain C57BL. In 1937, two subfamilies, C57BL/6 and C57BL/10, were isolated from C57BL. In 1985, the strain was sent from Olac to the Institute of Laboratory Animals of the Chinese Academy of Medical Sciences. In April 2015 and again in June 2018, Vital River imported the strain from the National Rodent Laboratory Animal Seed Center.