Dragon's Gate by Laurence Yep
It is February 1867, and Otter has come from China to San Francisco, California—the Land of the Golden Mountain to join his father and uncle. Where Otter expected to see a land of goldfields, he sees only vast, cold whiteness. But his dream is to learn all he can, take the technology back to the Middle Kingdom, and free China from the Manchu invaders. He boards a machine that will change his life—a train—in this gripping novel set during the building of America's transcontinental railroad.