Tin Pan Alley originally referred to a specific place: West 28th Street between Fifth and Sixth Avenues in the Flower District of Manhattan. It was the location of New York City music publishers and songwriters who dominated the popular music of the United States in the late 19th century and early 20th century.
In the mid-19th century, copyright control of melodies was not as strict, and publishers would often print their own versions of the songs popular at the time. With stronger copyright protection laws late in the century, songwriters, composers, lyricists, and publishers started working together for their mutual financial benefit. Songwriters would literally bang on the doors of Tin Pan Alley businesses to get new material.
The start of Tin Pan Alley is usually dated to about 1885, when a number of music publishers set up shop in the same district of Manhattan. The end of Tin Pan Alley is less clear cut. Some date it to the start of the Great Depression in the 1930s when the phonograph, radio, and motion pictures supplanted sheet music as the driving force of American popular music, while others consider Tin Pan Alley to have continued into the 1950s when earlier styles of music were upstaged by the rise of rock & roll, which was centered on the Brill Building.
According to the Online Etymology Dictionary, 1882, "tin pan" was slang for "a decrepit piano" (1882), and the term came to mean a "hit songwriting business" by 1907.
The biggest music houses established themselves in New York City, but small local publishers – often connected with commercial printers or music stores – continued to flourish throughout the country, and there were important regional music publishing centers in Chicago, New Orleans, St. Louis, and Boston. When a tune became a significant local hit, rights to it were usually purchased from the local publisher by one of the big New York firms.