In 1859, a newly organized group of Mennonites in Iowa invited any interest Mennonites to join them in forming a union to work together to promote missions. The invitation was published in "Das Christliche Volksblatt" with Oberholtzer endorsing the idea. A formal meeting took place on 29 May 1860, resulting in the creation of the General Conference Mennonite Church. Oberholtzer was a key committee member in drawing up the organization's constitution and presided over four of the initial sessions. When Daniel Hege visited Pennsylvania the following year to explain the purpose of the new conference, Oberholtzer's own East Pennsylvania Conference joined and would become the Eastern District Conference within this new structure.