What a gorgeous coin. This one comes from a time when they knew how to get real artwork on to a coin. They were not encumbered by political correctness and pet projects.
Wikipedia: The Panama-Pacific International Exposition (PPIE) was a world's fair held in San Francisco, in the United States, between February 20 and December 4 in 1915. Its ostensible purpose was to celebrate the completion of the Panama Canal, but it was widely seen in the city as an opportunity to showcase its recovery from the 1906 earthquake.
(Note to inquirer Joel: You did not give us enough information to accurately identify your coin. There many commemorative medals made as well. We do not know of a one dollar coin minted in silver.)
If you have one of these beauties, the coin catalogs are kind to it:
worn: $80 US dollars approximate catalog value
average circulated: $150
well preserved: $200
fully uncirculated: $500
You can see that condition means a lot to the value of this coin. Convert these catalog values to actual buy and sell values using our Important Terminology page.