Is Isa brown a crossbreed chicken?

Yes, Isa Brown is a crossbreed chicken. It is a hybrid of the Rhode Island Red and the White Leghorn chicken breeds, developed in the 1950s in the United Kingdom by the Institute of Animal Physiology in Babraham, Cambridge, from lines maintained at the Houghton Poultry Research Station. Isa Brown chickens are known for their excellent egg-laying abilities, and they are commonly used in commercial egg production.