<P> A minority of Chinese immigrants did not join the CCBA as they were outcasts or lacked the clan or family ties to join more prestigious Chinese surname associations, business guilds, or legitimate enterprises . As a result, they organized themselves into their own secret societies, called Tongs, for mutual support and protection of their members . These first tongs modeled themselves upon the triads, underground organizations dedicated to the overthrow of the Qing dynasty, and adopted their codes of brotherhood, loyalty, and patriotism . </P> <P> The members of the tongs were marginalized, poor, had low educational levels and lacked the opportunities available to wealthier Chinese . Their organizations formed without any clear political motives and soon found themselves involved in lucrative criminal activities, including extortion, gambling, people smuggling, and prostitution . Prostitution proved to be an extremely profitable business for the tongs, due to the high male - to - female ratio among the early immigrants . The tongs would kidnap or purchase females (including babies) from China and smuggle them over the Pacific Ocean to work in brothels and similar establishments . There were constant internecine battles over territory, profits, and women in feuds known as the tong wars, which began in the 1850s and lasted until the 1920s, notably in San Francisco, Cleveland and Los Angeles . </P> <P> The Chinese came to California in large numbers during the California Gold Rush, with 40,400 being recorded as arriving from 1851 to 1860, and again in the 1860s when the Central Pacific Railroad recruited large labor gangs, many on five - year contracts, to build its portion of the Transcontinental Railroad . The Chinese laborers worked out well and thousands more were recruited until the railroad's completion in 1869 . Chinese labor provided the massive labor needed to build the majority of the Central Pacific's difficult railroad tracks through the Sierra Nevada mountains and across Nevada . The Chinese population rose from 2,716 in 1851 to 63,000 by 1871 . In the decade 1861--70, 64,301 were recorded as arriving, followed by 123,201 in 1871--80 and 61,711 in 1881--90 . 77% were located in California, with the rest scattered across the West, the South, and New England . Most came from Southern China looking for a better life; escaping a high rate of poverty left after the Taiping Rebellion . This immigration may have been as high as 90% male as most immigrated with the thought of returning home to start a new life . Those that stayed in America faced the lack of suitable Chinese brides as Chinese women were not allowed to emigrate in significant numbers after 1872 . As a result, the mostly bachelor communities slowly aged in place with very low Chinese birth rates . </P> <P> The last major immigration wave started around the 1850s . The West Coast of North America was being rapidly colonized during the California Gold Rush, while southern China suffered from severe political and economic instability due to the weakness of the Qing Dynasty government, internal rebellions such as the Taiping Rebellion, and external pressures such as the Opium Wars (1839--1860). As a result, many Chinese emigrated from the poor Taishanese - and Cantonese - speaking area in Guangdong province travelled to the United States to find work . </P>

When did the chinese work on the railroad