Latin America Mission first developed its Evangelism-in-Depth (E/D) program in 1959, following a decade-long series of citywide evangelistic campaigns from 1949 to 1958. Growing out of the mission's long evangelistic history beginning in 1921, E/D became a model that missionaries and missiologists around the world used in the 1960s and early 70s. E/D shifted the focus of evangelism from presenting a single professional evangelist in a one-time event to a countrywide, congregation and laity-based, year-long effort. The E/D program for a country consisted of organized prayer, training for lay Christians, preparation for counselors, follow-up of new Christians, widespread publicity, door-to-door visitation, local and regional evangelistic meetings, regional and national parades, youth meetings (illustrated by the poster above in Bolivia) radio and television programs, and widespread Bible and tract distribution. E/D flourished on a broad scale until 1971 in fourteen Latin American countries, continuing afterward in Mexico. In the late-1960s LAM opened its Office of Worldwide Evangelism-in-Depth to promote the program's use outside Latin America.

The records of Latin America Mission include many documents that help trace the development and influence of Evangelism-in-Depth, as well as the history of the mission, other efforts to spread the Gospel, and the religious environments in Latin America (primarily in Colombia and Costa Rica).