Complex sentence: The oldest Evangelical Synod congregation is believed to be either Bethlehem Church in Ann Arbor, Michigan, founded in 1833, (this congregation remains affiliated with the UCC to this day), or Saint John's-Saint Luke Evangelical and Reformed UCC in Detroit Michigan.
Split into simpler sentences: The oldest Evangelical Synod congregation is believed to be either Bethlehem Church in Ann Arbor, Michigan, founded in 1833. This congregation remains affiliated with the UCC to this day, Or Saint John's-Saint Luke Evangelical and Reformed UCC in Detroit Michigan.