To what fair does the song “Meet Me in St. Louis” refer?

The song “Meet Me in St. Louis” by Andrew B. Sterling and Kerry Mills refers to the 1904 Louisiana Purchase Exposition in St. Louis, Missouri.

The tune provides the leitmotif for the 1944 musical film Meet Me in St. Louis, starring Judy Garland, about a St. Louis family faced with a move to New York just as the 1904 Exposition is about to open.