The American Cocker is one of the nine spaniel breeds which are all members of the sporting dog group. The history of the breed dates back to fourteenth century Europe, where the dogs were known as "spanyells" and they were bred for hunting to flush and retrieve game for their owners.

They were found in France and Switzerland but are believed to have originated in Spain. When introduced into England the spaniel breed began to form the spaniels that we know today.

The English Cocker, the English Springer Spaniel and what has become the American Cocker all share the same heritage. In the early 1800's there were two popular English spaniels of which one was the ancestor of today's English Springer Spaniel and the other a smaller cocking spaniel (referring to its specialty in hunting woodcocks). The main difference between the two popular Spaniels were their size and up until the 1870's the only qualification for a Cocker Spaniel was to weigh under 25 pounds.

In 1879 it is believed that the dog that has been looked at as the father of the English Cocker Spaniel, Obo, was born and by 1892 the Cocker Spaniel and the Springer Spaniel were recognized as distinct and separate breeds by the Kennel Club of England.

In 1881 the American Spaniel Club was formed to satisfy the needs of the large amount of breeders in North America but nevertheless there still had been some interbreeding between the Cocker Spaniels and Springer Spaniels in North America as well as in England.

In the early 1900's Cockers had become a very popular breed in North America as they were wonderful family dogs, good game dogs and at the same time having great affection for their owners. During the 1920's, some physical differences were starting to be noticed with the American cockers as their muzzles had become smaller, they had a softer coat, and were lighter in weight. Due to these changes in 1935 the English Cocker Spaniel Club of America was formed to help discourage the interbreeding of the English Cocker and the American Cocker as up until this time the English Cocker had been the recognized breed but with the differences now between the two there had become a lot of confusion.

In 1946 the American Kennel Club officially recognized the American Cocker as a separate breed and thus the separation of the two different breeds of Cocker Spaniels: The English Cocker Spaniel and the American Cocker Spaniel.

Today, in the United States the Cocker is referring to the American Cocker Spaniel, while outside the United States the Cocker is referring to the English Cocker Spaniel.