When did the U.S. Postal service begin using zip codes?

 Announced on April 30, 1963, and put into effect on July 1, ZIP—or Zoning Improvement Plan codes gave the post office a better, more efficient way to sort mail. "The first digit designated a broad geographical area of the United States, ranging from zero for the Northeast to nine for the far West. This number was followed by two digits that more closely pinpointed population concentrations and those sectional centers accessible to common transportation networks. The final two digits designated small Post Offices or postal zones in larger zoned cities."

Source: http://mentalfloss.com/article/50450/50-things-turn-50-2013