The YTCA states the main 3 dogs used in the production of the Yorkshire terrier are
The Clydesdale Terrier, Old English (toy rough and broken haired)
Terrier and the Waterside Terriers.
The Waterside terriers are every interesting.
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Airedale Terrier
Airedale Terrier - The Early Days
1850 - 1910
The Airedale Terrier was formally known as the Waterside or Bingley terrier. It's roots can be traced back to the valley of the river Aire in Yorkshire district of Great Britain. It's most important ancestor was the local rough coated working terrier. Mostly black & tan with a fearless temperament and strong hunting instinct. Being a medium sized dog in general appearance for a terrier the Airedale was big. This gave him later the name "king of terriers". The Airedale was always a breed which was known for its versatile working abilities.
Around 1850 Mr. Holmes carefully crossed otterhound with the local working terrier to get a stronger and bigger dog with the brain, the temperament and the coat of the terrier and the retrieving ability, the nose and the qualities in water work of the otterhound. To better the breed other breeds like collies and bullterrier have been crossed in. Like the most other breeds too, the Airedale and his ancestors have been workers in those days and their look has rapidly changed in the last 150 years mostly because the show breeders got a hold of them.
So we have
Collie Tri-colored
Bull terriers Tri-colored