Explanation: From the year 1850 to 1900 the port of San Francisco became the main gateway to Chinese immigrants. It is known that many Chinese inmigrants arrived to the United States of America; the first time was before 1848. It was mainly due to the so called "California gold rush", thanks to it, a large number of workers from China arrived to extract the gold. They also worked in the construction of the transcontinental railroad and in the mines.
