The Evangelical Lutheran Synod of Illinois, often referred to as the Illinois Synod, was created in June 1846 when the Evangelical Synod of the West divided due to growth. It held its first convention in Hillsboro, Illinois, on October 15, 1846. To that end, in May 1880, the Illinois Synod merged with the Illinois District of the Lutheran Church–Missouri Synod, while urging its congregations in Missouri to join the Missouri Synod's Western District. At the time of the merger, the Illinois Synod had 26 congregations, 23 pastors, and 6,004 communicant members.