The Chinese emigrants onboard the SS Japan had not only been involved in the California Gold Rush — which led to the extraction of an estimated $2 billion worth of gold up to 1855 — some had spent three or four years building the US transcontinental railway and the US' first irrigation system.

The migration of these early Chinese to the US started with California. Wells described how The Six Companies, or the Chinese Consolidated Benevolent Association, helped their provincial countrymen from Sze Yup and Sam Yup districts of Guangdong to come to the US. Ships brought this first generation.

He added that the second wave of Chinese emigration picked up in the late 1860s and into the 1870s with the advent of the Pacific Mail transpacific steamer service.

Included in this second wave were the Guangzhou (Canton) merchants that established a Chinatown in San Francisco in the 1850s. They built churches and banks, helped complete the railroad in 1869, and expanded the textile and tea trade with the eastern US.

From 1867 to 1875, the US was working with the Qing Dynasty (1644-1911) through US Ambassador Anson Burlingame, which led to the Burlingame-Seward Treaty in 1868.

The treaty not only eased immigration restrictions, it guaranteed laborers for US firms, lessened US interference in internal Chinese affairs and encouraged diplomacy.

Spurred by the treaty, US President Abraham Lincoln was partly responsible for the construction of the SS Japan.

In 1865, Lincoln signed a bill into law that established a transpacific oceanic mail service. He wanted to aid in the completion of the transpacific railroad and develop trade relations with China.

The SS Japan, built in New York, was one of four steamships responsible for transporting tens of thousands of Chinese laborers to the US. All four were officially authorized to be constructed in Greenpoint, Brooklyn by Lincoln in February 1865, just weeks before his assassination in April 1865.

When finished, famous American writer Mark Twain called the SS Japan, a "perfect palace of a ship". It began sailing to China from San Francisco a few years later.