"China town" was originally a California term for a town where Chinese workers (usually railroad workers) lived.
A Chinatown is historically any ethnic enclave of Chinese or Han people outside China, Taiwan and Singapore. Areas known as "Chinatown" exist throughout the world, including the Americas, Europe, Africa, Australasia and Asia.
In the Americas, which includes North America, Central America and South America, Chinatowns have been around since the 1800s. The most prominent ones exist in the United States and Canada in New York City, San Francisco, Vancouver, and Toronto. New York City is home to the largest ethnic Chinese population outside of Asia, including several Chinatowns in and around Manhattan, Flushing, and Brooklyn. There is also a Little Fuzhou developing in Manhattan and in a nearby area of Brooklyn.
(Oxford English Dictionary)
A section of a large town, especially a sea-port, in which Chinese live as a colony and to a great extent follow their own customs.
1857 Butte Record (Oroville, Calif.) 31 Jan. 2/7 Chinatown was wild with joy.
24 July 1858, Weekly San Joaquin Republican (Stockton, CA), pg. 1:
The "Melican" spread himself by kicking at the door of China Town.
9 April 1859, Chicago Press and Tribune, "Chinese in California," pg. 2:
About 200 miners at once responded, and the few Celestials who did not run away at once from fright were taken into the town of Shasta, marching between two files of armed miners, and dismissed at China-town, wit hthe warning that they should not again attempt to work in districts where the miners' local laws forbade.
18 July 1859, Mountain Democrat (Placerville, CA), pg. 2:
Rubbish on Denham Street (China town) above the bridge.
13 June 1860, New York Times, pg. 3:
On the 10th of June the volunteers returned to Chinatown and disbanded.
(In San Francisco -- ed.)