The "Golden Spike" refers to the ceremonial final spike driven into the last tie of the First Transcontinental Railroad in the United States. This event took place on May 10, 1869, at Promontory Summit in Utah. The spike was made of gold and symbolized the completion of a significant engineering achievement that connected the eastern and western parts of the country. The completion of the railroad greatly facilitated transportation and commerce, allowing goods and people to move more efficiently across the nation. The event marked a pivotal moment in American history, contributing to the expansion and economic growth of the United States.