Why?
Many Chinese came to America because of famine and poverty during the Qing dynasty. Then came a rebellion in the 1840's that would last 20 years and 30 million lives. They were pulled to America because of the gold discovered in California, and many came with hopes of becoming rich and sending money back to China for their families.
The Journey
They were the main group of immigrants to come from the Pacific, which was a longer journey the Europeans had to take. Many settled in Hawaii. They mainly came to San Francisco in search of making a living off of gold.
In the US
Besides being miners, they also sought to become entrepreneurs. Many became laborers that helped build the Transcontinental Railroad. They were despised by many Americans, and large groups of Anti-Chinese wanted them deported. The government in California even passed a law making it more difficult for them, breaking a treaty made with China. This caused political problems.
Influence in the US
They were the main contributors of the Transcontinental Railroad, as many of the Chinese immigrants were laborers. When examining the need for a Railroad from coast to coast, one can see that the increasing population in the west was the reason. When you look deeper, you can see that a large percentage of that growing population was Chinese. They also played a major role in shaping Hawaii's and California's culture.