I believe the German Reformed Church merged with the Evangelical Church in the United States to form the Evangelical and Reformed Church, which in turn merged in the mid-20th century with the Congregational Church to form the present-day United Church of Christ. You can read about them all at <www.ucc.org/aboutus/shortcourse/index.shtml>. Presbyterian archivists/historians may be able to tell you how common it was for their churches to accept a non-Presbyterian as pastor. Maybe he was the only game in town/port in a storm/other bad analogies, so they left him preach. My relative was a Presbyterian elder in Neoga starting around 1870; I've read the original minutes of the elders' meetings, and they sound as though anyone who was not a signed/sealed/and delivered Presbyterian was going straight to a much warmer climate.