Plymouth Rocks were developed from a cross of Dominique males and either Black Java or Black Cochin females. The original Plymouth Rock had a barred plumage pattern and was considered the most popular breed in the United States in the early 20th Century, used for both meat and brown egg production. White Plymouth Rocks are the result of white sports of the barred variety. White Plymouth Rock chicks are smoky light yellow. They have single combs and clean, black or gray legs and feet. The feathers of adult White Rocks are white, with yellow shanks and feet. The White Plymouth Rock is used in the Cornish x Rock crosses that was developed for meat production, however, most pure White Plymouth Rocks are used for large brown egg production.