Millions of Chinese left their home country in the past to go and to live abroad. Most of them have gone to other countries out of economic reasons. In past centuries Chinese abroad were treated badly and seen as cheap workers. They had jobs in farming, as cooks on ships or as harbour workers. In the US, thousands of Chinese helped to build the railroads that today span the continent. In previous times the United States and other countries limited the number of Chinese who could enter the country.