Plymouth Rock chicken
Plymouth Rock Hen
|Country of origin||United States|
|ABA||Single comb clean legged|
|PCGB||Soft feather: heavy|
|APS||heavy breed softfeather|
The Plymouth Rock is an American breed of domestic chicken. It was first seen in Massachusetts in the nineteenth century, and for much of the early twentieth century was the most popular chicken breed in the United States. It is a dual-purpose breed, raised both for its meat and for its brown eggs. It is resistant to cold, easy to manage, and a good sitter.:68
The Plymouth Rock was first shown in Boston in 1849, but was then not seen for another twenty years. In 1869, in Worcester, Massachusetts, one D.A. Upham cross-bred some Black Java hens with a cock with barred plumage and a single comb; he selectively bred for barred plumage and clean (featherless) legs.:68 His birds were shown in Worcester in 1869; the modern Plymouth Rock is thought to derive from them. 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.
In 1888, the White Plymouth Rock was created through selective breeding in the hopes that it would be a superior meat producing bird. It quickly eclipsed the Barred Rock in popularity and became the leading broiler chicken in countries like the United States and Australia.  Industries still use the White Plymouth Rock as one of their main producers of meat.  
The Plymouth Rock is listed by the Livestock Conservancy as "recovering", meaning that there are at least 2500 new registrations per year. Worldwide, numbers for the Plymouth Rock are reported at almost 33,000; about 24,000 are reported for the Barred Plymouth Rock, and over 970,000 for the White variety.
The Plymouth Rock has a single comb with five points; the comb, wattles and ear-lobes are bright red. The legs are yellow and unfeathered. The beak is yellow or horn-colored.:69 They have long, broad backs with moderately deep, full breasts. Their feathers are loose compared to other chickens and they lay brown eggs. They are winter-hardy, broody birds that are usually tame and docile but can become aggressive under stressful circumstances.
In the United States, seven color varieties of the Plymouth Rock are recognized: Barred, Blue, Buff, Columbian, Partridge, Silver-penciled and White. Ten plumage varieties are listed by the Entente Européenne d’Aviculture et de Cuniculture, of which five – Barred, Black, Buff, Columbian and White – are recognized by the Poultry Club of Great Britain. In Australia, the Barred variant is split into two separate colors, Dark Barred and Light Barred.
Plymouth Rock Chickens are commonly used for mass egg and meat production. Specifically, the White Plymouth Rock because it has been selectively bred for industrial production and studies suggest they statistically yield more eggs and meat compared to other variations of the Plymouth Rock.  In addition, their docile nature and hardiness make them an easily mass produced and raised species. Barred Plymouth Rocks are seeing negative population trend in industries while White Plymouth Rocks are seeing a sharp positive trend.
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- Plymouth Rock Chicken The Livestock Conservancy. Archived 10 October 2016.
- APA Recognized Breeds and Varieties: As of January 1, 2012. American Poultry Association. Archived 4 November 2017.
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- Transboundary breed: Plymouth Rock White. Domestic Animal Diversity Information System of the Food and Agriculture Organization of the United Nations. Accessed October 2016.
- James Bishop (1998). Australian Poultry Standard, first edition. Linton, Victoria: Victorian Poultry Fanciers' Association. ISBN 9780646362311.
- Bujko, Jozef; Hrnčár, Cyril; Hric, Peter (2012-05-31). "Diversity in Population Size and Production Parameters of Selected Varieties of Plymouth Rock Chicken Breed". Scientific Papers Animal Science and Biotechnologies. 45 (1): 189–192. ISSN 2344-4576.