Each black dot represents the geometric center of a ZIP code. Matt Stiles/U.S. Census Bureau hide caption itoggle caption Matt Stiles/U.S. Census Bureau The Two-Way The ZIP Code Turns 50 Today; Here Are 9 That Stand Out July 1, 2013 The U.S. Postal Service began using the five-digit ZIP code in 1963. In recognition of the anniversary, we've examined the list of more than 40,000 ZIP codes and highlighted a few that deserve extra attention.