<Ul> <Li> 1840s--1860s--Many initial Chinatowns developed in the west spurred by the California Gold Rush and the Transcontinental railroad, such as San Francisco's Chinatown . </Li> <Li> 1863--Emancipation Proclamation opens up new opportunities for Chinese in the Southern United States </Li> <Li> 1860s, 1870s, 1880s--racial tensions, labor tensions, leads to incidents such as the Rock Springs Massacre </Li> <Li> 1882--1943--Chinese Exclusion Act was in effect, banning Chinese immigration into the United States . </Li> <Li> 1943--Repeal of Chinese Exclusion Act, Chinatown populations start to rise again . </Li> <Li> 1970s--end of Vietnam War </Li> <Li> 2010s--Downturn of US . economy, China economy rises, causes reverse migration, and decay of Chinatowns </Li> </Ul> <Li> 1840s--1860s--Many initial Chinatowns developed in the west spurred by the California Gold Rush and the Transcontinental railroad, such as San Francisco's Chinatown . </Li> <Li> 1863--Emancipation Proclamation opens up new opportunities for Chinese in the Southern United States </Li> <Li> 1860s, 1870s, 1880s--racial tensions, labor tensions, leads to incidents such as the Rock Springs Massacre </Li>

How many chinatowns are there in the united states