In what state was the first transcontinental railroad completed in 1869, with the hammering of the Golden Spike?

The golden spike (also known as The Last Spike) is the ceremonial final spike driven by Leland Stanford to join the rails of the First Transcontinental Railroad across the United States connecting the Central Pacific and Union Pacific railroads on May 10, 1869, at Promontory Summit, Utah Territory. The spike now lies in the Cantor Arts Center at Stanford University.

The spike had been manufactured earlier that year especially for the event by the William T. Garratt Foundry in San Francisco. Two of the sides were engraved with the names of the railroad officers and directors. A special tie of polished California laurel was chosen to complete the line where the spike would be driven. The ceremony was originally to be held on May 8, 1869 (the date actually engraved on the spike), but it was postponed two days because of bad weather and a labor dispute that delayed the arrival of the Union Pacific side of the rail line.

On May 10, 2006, on the anniversary of the driving of the spike, Utah announced that its state quarter design would be a depiction of the driving of the spike. The Golden Spike design was selected as the winner from among several others by Utah's governor, Jon Huntsman, Jr., following a period during which Utah residents voted and commented on their favorite of three finalists.