In addition to general circulation coins, the US also mints a lot of commemorative coins. The first generally accepted commemorative coin minted by the US government was a half-dollar first struck in 1892 in conjunction with an event that was held between May and October, 1893, in which city? (For a dollar, you could buy this half-dollar, but they generally sell for a lot more money today!)
Chicago (World's Columbian Exposition)