The American Staffordshire Terrier, also known as the Amstaff, isis a medium-sized, short-coated American dog breed. It is one of several breeds in the pit bull group. In the early part of the twentieth century the breed gained social stature and was accepted by the American Kennel Club in 1936 and should not be confused with the Staffordshire Bull Terrier of the United Kingdom.

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The Staffordshire Terrier's ancestor, the bull and terrier was first bred in the nineteenth century in Birmingham. The early ancestors of this breed came from England where, until the first part of the 19th century, the Bulldog was bred. Bulldogs pictured as late as 1870 resemble the Staffordshire Terrier's ancestor, the contemporary American Staffordshire Terriers, to a greater degree than present-day Bulldogs. Some writers contend it was the White English Terrier, Fox Terrier, or the Black and Tan Terrier that was crossed with the Bulldog to develop the Staffordshire Bull Terrier; all three breeds shared many traits, the greatest differences being in color and spirit. The cross of Bulldog and Terrier was called by several names, including Bull-and-Terrier Dog, "Pit Bull Terrier" (Bull terrier used to fight on pit), or Half and Half.

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The American Staffordshire Terrier should give the impression of great strength for his size, a well put-together dog, muscular, but agile and graceful, keenly alive to his surroundings. He should be stocky, not long-legged or racy in outline. Height and weight should be in proportion. A height of about 18 to 19 inches (46 to 48 cm) at shoulders for the male and 17 to 18 inches (43 to 46 cm) for the female is to be considered preferable.