The UAIM was created under the sponsorship of the Committee on Cooperation in Latin America, a multi-denominational agency that served as an umbrella organisation for all liberal Protestant missions in the region.
Prominent missionaries working for the UAIM were, among others, Paul Streich, Benjamin Gutiérrez and Eugene Braun.
The first missionary field for the UAIM was Picalquí, in Pichincha, Ecuador, where the mission bought a farm to train the amerindian people living there in agricultural techniques.
When the mission disbanded (due to disagreements among its missionaries and also because of the strong anti-American feelings among Ecuadorian church leaders), it had few congregations.
Gonzalo Carvajal, who resigned to work for HCJB and the Presbyterian Church in America (PCA).