During the 1840s the planet experienced another "gold rush", although not as famous as the California one: it was a rush to mine minerals in the Chinese province of Yunnan, which drew millions of Chinese immigrants to the sparsely populated region. The flow of people between Yunnan and the Pearl River delta (Canton and Hong Kong) spread more than minerals and opium: a plague that had started in Yunnan reached Canton and Hong Kong in 1894, killing 100,000 people in a few weeks. Millions died in India between 1896 and 1898 and in Manchuria in 1899. It reached Hawaii in December 1899 (where Chinatown was burned down accidentally in an attempt to burn infected houses) and then ships started arriving in San Francisco with dead sailors. All ships from China, Japan, Australia and Hawaii were ordered to fly yellow flags and were quarantined, but the plague found its way into Chinatown anyway in February 1900. California's governor Henry Gage, fearful of the economic consequences if panic spread throughout the state, hesitated to lock down Chinatown even after the scientists confirmed the plague beyond any reasonable doubt, even criminalizing epidemiologist Joseph Kinyoun, censoring newspaper reports of plague infections, spreading disinformation and refusing to administer Waldemar Haffkine's experimental vaccine (note the similarities with 2020 when US president Donald Trump hesitated to recognize the covid pandemic and epidemiologist Anthony Fauci was even criminalized by right-wing media that also conducted anti-vaccine campaigns). The result was that the plague kept spreading and killed more than 100 people in the city. The worst consequence, however, was that it further increased anti-Chinese sentiments among Whites. In 1901 San Francisco's own mayor James Phelan wrote an article titled "Why the Chinese Should Be Excluded".

Jack London himself, one of the most progressive writers of the time, depicted the ethnic Chinese population as an existential threat to the USA in the essay "The Yellow Peril" (1904) and conveyed his fear that China would some day conquer the world in the short story "The Unparalleled Invasion" (1910). London, who had visited Japan in 1893 and Manchuria in 1904 (as a reporter covering the Russo-Japanese War), predicted the rise first of Japan as a military and industrial power, the Japanese invasion of China, and then the rise of China as a military and economic power (60 years before Japan became the second world economy and 100 years before China passed Japan!)

That was just the tip of the iceberg. The bad reputation of Chinatown as a den of sin, crime and prostitution, and now also of disease, was unique in California at a time when San Francisco was trying to promote itself as a modern city, on par with the most fashionable European cities.

Sinophobia was widespread in the Anglo-Saxon world and in fact the term “yellow peril” originated in Britain, with Matthew Shiel’s novel “The Yellow Danger” (1898). The anti-foreign and anti-Christian "Boxer Rebellion" that raged in China from 1899 to 1901 was misrepresented in Britain and the USA. The American Federation of Labor, the largest union of the USA, published a pamphlet titled "Some Reasons for Chinese Exclusion - Meat vs. Rice - American Manhood Against Asiatic Cooliesm, Which Shall Survive?" (1902).

The Japanese, who were migrating from both Hawaii and Japan to replace the Chinese in the farms, didn't fare much better: in 1906 San Francisco even ordered 93 Japanese schoolchildren who were attending public schools to enroll in the segregated "Oriental School" of Chinatown, an international incident after which the US president convinced the Japanese government to curb emigration to California (the "Gentlemen's Agreement" of 1907).

In April 1906 San Francisco was destroyed by an earthquake and a fire. Many of the great mansions and historical buildings were reduced to rubble.

Chinatown suffered perhaps more than any other neighborhood. The disaster made news all over the world and in particular in China. The Chinese minister Liang Cheng arrived in Oakland to lead a relief effort, another gesture of solidarity from the homeland.

California's politicians, instead, saw a chance to get rid of Chinatown. A special "Subcommittee on Relocating the Chinese" was convened, with the intention of kicking the Chinese out of the city and giving their land to real-estate speculators. China's empress Cixi had to sent her ambassador to San Francisco to defend the ethnic Chinese. The Six Companies pointed out the economic damage that would be caused by losing the lucrative Asian trade and the cheap laborers. But ultimately the project of deporting the Chinese failed for a simpler reason: at the peak of anti-Chinese sentiment, no other city was willing to accept new Chinese residents. In October 1906, amidst anti-Japanese sentiment, San Francisco renamed the Chinese School the "Oriental Public School" (with all Caucasian teachers), and the 93 ethnic Japanese schoolchildren of the city's public schools were moved to it.

And so the Chinese started rebuilding Chinatown, and by 1908 their work was done while the rest of the city was still under reconstruction. The new Chinatown was very different from the old one. The old one was basically an unappealing slum of filthy wooden tenements. The new one was designed by architects (hired by Chinese merchants) with the deliberate intention of creating a Chinese-themed tourist attraction. Hence the iconic pagoda-topped buildings of the Sing Chong and Sing Fat bazaars. That's when Look Poong-shan (born in Mendocino of a wealthy Chinese merchant man and an "Indian" woman), originally employed at the San Francisco branch of the Russo-Asiatic Bank, founded in Chinatown the first Chinese bank in the USA, the Canton Bank. The best thing about the new Chinatown was that the earthquake and fire crippled the tongs.

The Exclusion Act all but killed Chinese immigration into California. Indirectly, it redirected Chinese immigration to the East Coast: in 1892 the US government opened the immigration station at Ellis Island in New York through which millions of Europeans arrived. Despite the Exclusion Act, thousands of Chinese were admitted and set off the creation of Chinatowns of the eastern cities (New York, Boston, etc). This was an important moment in the history of US immigration because previously immigration was delegated to each state. The millions of new (mainly European) immigrants convinced the US government of the need for a national immigration policy.

There was another loophole that allowed the Chinese to immigrate specifically to California. The partial good news out of the 1906 earthquake was that the city's records were also destroyed so that any immigrant could claim to be a citizen. Many Chinese who were not citizens did so and became US citizens overnight. That allowed them to bring their immediate family members from China to the USA.

Discrimination against the Chinese continued unabated, but now the Japanese, who had replaced the Chinese in the countryside, were perhaps targeted even more viciously. The 1907 riots in San Francisco affected the Chinese but were actually started by anti-Japanese activists.

California didn't have the equivalent of Ellis Island until 1910 when the old military reserve of Angel Island, in the middle of the San Francisco Bay, was turned into an immigration station. That became the arrival point of Chinese immigrants. Because of the Exclusion Act, they were often detained there for weeks while the bureaucrats decided if they were arriving legally (as family members of US citizens) or not. The Chinese immigrants spent days and nights in the public dormitories of the island (which are still covered with graffiti, including 200 poems).

In 1913, California passed another discriminating law: the Alien Land Law, which limited the right to own land to "foreigners eligible to become citizens". Asians were not eligible under the Naturalization Law of 1870. The law (not repealed until 1952) was mainly directed against the Japanese, who now controlled most of the agriculture in California, but de facto kept the Chinese from buying land outside their own Chinatowns.

During the "exclusion years", the Chinese emigrants, who in the 1850s had mainly headed for California and Australia, often opted for the British colonies of east Asia, like Singapore, where the British needed laborers.