1966: OPC Committee to Confer with Representatives of the Christian Reformed Church proposes working toward organic union with CRC.1
March 19, 1969: Joint OPC-RPCES gathering at Calvary Reformed Presbyterian Church, Willow Grove. Edmund Clowney (OPC) and Robert Rayburn (RPCES) speak on “The Urgency of Our Times and the Question of Union."2
1972: Formal committee planning begins for OPC-RPCES merger.3
April 24, 1973: OPC Presbytery of the Midwest and RPCES Midwestern Presbytery meet in St. Louis to discuss proposed union.4
June 1973: Both OPC and RPCES assemblies approve sending Plan of Union to presbyteries for discussion.5
December 4-7, 1973: First general assembly of the PCA.6
January 21, 1975: OPC Committee on Ecumenicity and RPCES Committee on Fraternal Relations finalize proposed Plan of Union to form “Reformed Presbyterian Church."7
June 5, 1975: OPC votes 95-42 in favor of union with RPCES; RPCES votes against merger.8
1975: North American Presbyterian and Reformed Council (NAPARC) formed with PCA, OPC, RPCNA, RPCES, and CRC as charter members.9