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United States Postal Service - Wikipedia
About the United States Postal Service - Who we are - About.usps.com
United States Postal Service | History, Evolution, & Tracking
Board of Governors of the United States Postal Service
Postal History - Who we are - About.usps.com
History of the United States Postal Service - ThoughtCo
Postal history - Postal Facts - U.S. Postal Service
Home - About.usps.com
Introduction to Postal Facts - Postal Facts - U.S. Postal Service
United States Post Office Department - Wikipedia