In the early 1840s, James W. Marshall, living in Missouri, contracted malaria. In OTL, he moved west on the advice of his doctor. However, in ATL, he refused, and ended up dying. Thus their was no one to discover gold in California, and the Gold Rush never occurred. After the United States gained California, there was nothing it could do with it. There were no large cities, and no natural assets to speak of. Because of this, the California Territory faded into obscurity, and by the turn of the century, it was an agricultural outpost of the United States.