Promontory was a bustling place in the 1800s, home to crews who worked for Central Pacific or Union Pacific. The Golden Spike Ceremony on May 10, 1869 was held to officially recognize the meeting of the two railroads, making train travel possible from Nebraska all the way to Cali. Pretty huge deal back then. Click here to get the full history.
The actual golden spike and three other ceremonial spikes were presented to bigwigs, not driven into the ground like I thought, and like Stephen says is one of the biggest misconceptions. Bummer. Still, the museum is full of awesome finds from the period and the replicas of the original trains run all summer.
Dirt path most of the way up, once you get past ATK's facility in Corinne, but beautiful area. Make sure you bring some cash with you for the entrance fee: $7 per vehicle, $4 per motorcycle or bike...free per press pass. Yes!
I brought my camera for photos of the actual spot the ceremony was held, the trains themselves and the workshop where Stephen and the other engineers spend all winter cleaning/fixing the trains for summer reenactments.