Pork pie hat is round hat known from 19th century. That name is, logically, because the hat could look like pork pie dish which was seen in the 19th century in the window of every local baker in English. It is believed that smooth dark brown pork pie hat was the one most seen - there is a similarity with pork pie dish most effective.
These hats with its crease of the crown and the narrowness of the brim are also called "stingy brim" hats because of its brevity that made them "pork pies".
There are several periods of this hat, historical classified:
1) 1830-1865 - Pork pie hat was popular from 1830 through American Civil War. Usually was worn with feathers attached to a bow. It was made of felt, cotton canvas covered in silk, and even by the straw. Crown of this hat was low, and hat had a narrow brim that is the same width all the way around the hat. It is said that Americans brought back that style to America after they saw it on Englishmen (and ladies also) in the tennis matches. After that, pork pie hats were seen everywhere: from polo matches to the universities.
2) Buster Keaton period and the 1920s - In this period, the hat had a very flat top and brim. Thanks to Buster Keaton, a silent movie actor who wore this hat in his films, pork pie hat was again most wanted hat in the USA. This actor even made pork pie hat from other models of a hat, especially by Fedora, and the story said that he had thousand of them. At this time, pork pie hats were equally fashioned in Britain and the United States.
3) 1930's and 1940's - During Great Depression pork pie hat was again current. It had snap brim again, but this time was slightly increased in height. The dished top of hat could pop up, so it also was called "telescopic crown" or "tight telescope". By 1944, pork pie hat was also popular in New Guinea. Among African Americans, pork pie hat was part of the zoot suit, especially when was with feathers. During this time Frank Lloyd Wright wore this hat, but the most remembered is saxophonist Lester Young.
4) After 1950's - Although it was no longer so popular, pork pie was still worn mostly because it was considered as part of the zoot suit, and with that, it was connected to whole African American music scenes, such as jazz and blues. After the death of jazz saxophonist Lester Young (who wore it on stage during his lifetime), Charles Mingus, the musician, composed an elegy for him called "Goodbye Pork Pie Hat". Between 1951 and 1955 this hat was seen on television as a part of the wardrobe of many celebrities such as Art Carney and Joaquín Monserrat. In Jamaica, during 1960's it was popular as the "rude boy" subculture, but it also brought back popularity for this hat in Britain. One of his most famous wearers at that time was Yogi Bear, cartoon character. After 1960's, Gene Hackman wore this hat in the 1971 film The French Connection and in 1973 Robert de Niro in the movie "Mean Streets". One sort of pork pie hat is still worn by sailors in the United States and the United Kingdom as a part of the uniform.
Even today this hat is associated with 1930's, and 1940's so it's part of hipster fashion, and it's also recognized as Tom Waits or Johnny Thunder type of hat.