This series is broken down into two subgroups: personal and professional. Personal correspondence runs 1918-1939, 1950-1959, n.d. The majority of the personal correspondence contains the courtship letters between Eva and Leo while she taught graded school in Nebraska while he pursued further education in Iowa. Their correspondence continues through their early years of marriage and the birth of children while Leo traveled on work-related concerns. Other personal correspondence involves various extended family members and college friends of Leo. Professional correspondence deals solely with Leo's Chemurgic consulting and investment interests. It spans 1940-1955, 1959.

Both the personal and professional subgroups are arranged first alphabetically by correspondent, then chronologically.