As German speaking services were eliminated during World War II and sensing the need for younger leadership, Rev. Blemker resigned in May of 1946 and two months later, Rev. Dr. Karl Koepke accepted a call to become the church’s ninth pastor. Under his leadership, the church’s already generous posture toward needs throughout the broader body of Christ and in the world grew to an even greater degree. This was expressed in making sacrificial contributions to the building of senior living homes, orphanages, and discipleship programs. Additionally, the church participated in relief efforts to war-stricken countries by sending clothes, shoes, and finances to aid with rebuilding projects. 

Through the generous donation of church members, the “Evangelist” stained glass windows were installed in the north wall of the sanctuary in 1948. Additional stained-glass windows were installed around the second story of the sanctuary as memorials to loved ones. 

In 1951, the church helped to purchase land on Market Ave. North between 31st and 32nd Streets to help establish Market Heights Mission Church. 

In 1959, after several years of development, there was a merger between the Evangelical and Reformed Church and the Congregational Christian Church. This merger represented over eight thousand churches and two million people. As a result, the church’s name was changed to “First United Church of Christ.”