In May 1869, the gold spike ceremony at Promontory, Utah, united the tracks of the Central Pacific and Union Pacific Railroads with the hope that the railroad would unite the country as it joined the world’s two great oceans. However, the rails did not yet span the United States from ocean to ocean until some months later, when in September the final link between San Francisco and Sacramento was completed near the Flour Mill of Jesus Vallejo, a short distance east of this location.