Franklin Mint – History of the US – Columbian Exposition – 1893 – 45mm – Proof Bronze Medal. April 21 – Drop in U.S. gold reserves below $100 million leads to financial panic; May 1-Oct. 30 – World’s Columbian Exposition acclaims the 400th anniversary of the discovery of America by Cristopher Columbus; Sept.16 – The Cherokee Strip opened to settlement.