The word spanyell is thought to date from the late 1100s when it was used to name a type of dog imported into England from Spain, with the span part of the word referring to the country of origin. Records from the mid 1300s show that selective breeding was already in place, with the breed being separated into two distinct types, called water spaniels and land spaniels.
By 1801, the smaller variety of land spaniel was referred to as the Cocker or Cocking Spaniel, so named for its use in flushing woodcock.
According to historical records, the first spaniel was brought to North America aboard the Mayflower which sailed from Plymouth, England and landed in New England in 1620. The first Cocker Spaniel recorded in America was a liver and white dog named Captain, who was registered with the American Kennel Club in 1878. In 1881, the American Cocker Spaniel Club was formed; it would later become the American Spaniel Club (ASC) and is now known as the oldest breed club for dogs in the United States. The task of the club was initially to create a standard to separate the Cocker Spaniel in America from other types of land spaniels, a task which would take over 20 years, only being completed in 1905.
The dog considered to be the father of the American Cocker Spaniel was sired by the dog considered to be the father of the English Cocker Spaniel. Ch. Obo was bred to Ch. Chloe II, who was shipped to America while she was pregnant. Once in the United States, she whelped a dog who became Ch. Obo II. He differed greatly from the modern breed, being only 10 inches (25 cm) tall and with a long body, but was considered to be an excellent dog of that era and became a popular sire.
Towards the end of the 19th century, the breed had become popular in America and Canada due to their dual use as a family pet and a working dog.
In the early 20th century the breeders on either side of the Atlantic had created different breed standards for the Cocker Spaniel and the breed gradually diverged from one another, with the two becoming noticeably different by the 1920s. The American Cockers by now had a smaller muzzle, their coats were softer and the dogs overall were lighter and smaller. The differences were so apparent that in 1935, breeders founded the English Cocker Spaniel Club and restricted breeding between the two types of spaniel. The two types of Cocker Spaniel in America were shown together as one breed, with the English type as a variety of the main breed, until 1946 when the American Kennel Club recognised the English Cocker Spaniel as a separate breed.