[2] Other people have been associated with the development of the Plymouth Rock, as have other chicken breeds including the Brahma, the Cochin (both white and buff), the Dominique and the White-faced Black Spanish.

[2] With the advent of industrial chicken farming, it was much used in the development of broiler hybrids but began to fall in popularity as a domestic fowl.

[14] In the United States, seven color varieties of the Plymouth Rock are recognized: barred, blue, buff, Columbian, partridge, silver-penciled and white.

[3] Ten plumage varieties are listed by the Entente Européenne d'Aviculture et de Cuniculture, of which five – the barred, black, buff, Columbian and white – are recognized by the Poultry Club of Great Britain.

[15] The Plymouth Rock is a dual-purpose breed and is kept both for its meat and for its large brown eggs, of which it lays about 200 per year.