The ceremony begins on May 10, 1869, as an eastbound Central Pacific locomotive and a westbound Union Pacific locomotive meet in Promontory Point, Utah, marking the completion of the first transcontinental railroad.
The men on the cowcatchers are ready to toast the driving of the golden spike.
The work had been brutal. At one stage, efforts to tunnel through the marble spine of a Sierra Nevada mountain consumed an entire year, as only eight inches a day of progress was possible.
So: a fabulous accomplishment. But this is also an early example of a photo op—the use of a picture as a means to an end. Folks back East could see, plain as day, that a train could take them all the way to California, where businessmen anxiously awaited their commerce.