Simple text and photograhs describe what happens to the letters that are mailed and what the postal service is. Contents: Working for the USPS -- Addresses and zip codes -- Postage -- In the mailbox -- Through the Post Office -- Processing mail -- Mail on the go -- More processing -- Out for delivery. Part of the "Everyday Mysteries" series. Interest Level: K-3 Reading Level: 3.1 ATOS Book Level: 3.1 AR Interest Level: LG AR Points: .5 AR Quiz: 148249EN Lexile Measure: 570 Lexile Code: NC (Non-Conforming Text).