The changes in technology that have affected mail delivery are a dynamic way to encourage students to think critically and make meaningful connections across historical eras. In the classroom, personal communication through the mail can become the "thematic glue" used across historical units to highlight the changes in everyday life caused by technological innovation. The post office initiated changes in streetlighting and crosswalks, stimulated the development of rural roads and highways, and provided passenger services on railways. Classroom teachers can use the activities and discussion questions to introduce students to this entity and its influence on our history. (Contains 1 table and 2 figures.)