The following is an extract from this excellent article by Bosphorus Kingdom Kennels.
"Study of the breed’s origin have uncovered Chihuahua-like images in many parts and times of the world, including China, Egypt, Europe, Malta, Mexico, and South America; some dating, perhaps, from the ninth century. Many historians have documented similar-appearing little dogs found in artifacts, written descriptions, and art works, including a 1400’s Botticelli painting in the Sistine Chapel!
Chihuahua history in the United States began in the mid-1800’s when Americans began acquiring the dogs in Mexico. Many were purchased from the area of Chihuahua, ergo, the breed’s name, Chihuahua. Both varieties were popular and the presence of a molera (open fontanel) was a breed characteristic.
Maxwell Riddle in This Is the Chihuahua, writes, “Whatever its origin, the mod- ern Chihuahua is a purely American dog. The American standard is world wide and probably every registered Chihuahua in the world traces to purely American blood. “ (#20, p26) In the Chihuahua Guide, author Hilary Harmar states that “the Chihuahua has been developed to its present standard by American breeders during this century (20th).” (#16, p19)
AKC recognized the breed in 1924.
The first three AKC registered Chihuahuas were Long Coats. (#26, p6) The Chihuahua Club of America was formed in February 1923 and adopted the breed’s standard.
“The AKC first recognized the varieties (with trophies) at the Sesqui-Centennial in 1926.” (#23, p42)
Smooth Coats and Long Coats were divided into varieties in 1952.
The standard has been revised several times; 1934, 1954, 1972, and 1990.