From the ECLA Website:
The LCMS, firmly rooted in confessional conservatism and relatively unchanged since its organization in 1846-47 as “The German Evangelical Lutheran Synod of Missouri, Ohio, and Other States,” held to a belief in the inerrancy of the Bible.
“Historical criticism,” an understanding that the Bible must be understood in the cultural context of the times in which it was written, was gaining ground in both Europe and America. Trouble was brewing in the LCMS as some seminary professors began to adopt historical critical methods in their classrooms. A new seminary president with experience in inter-Lutheran and ecumenical affairs was challenged by the new conservative synodical president. A three-year investigation ensued and the 1973 convention voted to censure the faculty. In 1974 the seminary president was suspended and many seminarians and faculty left the seminary to continue their work in another setting, forming “Seminex,” a seminary-in-exile. Meanwhile, a moderate movement in LCMS called Evangelical Lutherans in Mission (ELIM) was formed.
The issue of whether or not to ordain graduates of Seminex led to the removal of four district presidents at the 1975 convention, and by 1976 the moderates had gathered forces to form the Association of Evangelical Lutheran Churches (AELC). Approximately 300 congregations and 110,000 people moved into the AELC from LCMS with a stated goal from the beginning of promoting unity with the ALC and LCA.
In 1977 the LCMS decision to place fellowship with ALC “in protest” along with the AELC’s “Call to Lutheran Union” nudged the three church bodies, ALC, LCA and AELC, toward merger. The 1978 ALC and LCA conventions adopted resolutions aimed at the creation of a single church body. The AELC joined them, and the ALC-LCA Committee on Church Cooperation became the Committee on Lutheran Unity (CLU) in January of 1979.
Presiding Bishop David Preus (ALC), Bishop James Crumley (LCA) and President and later Bishop William Kohn (AELC) met with the CLU over the next 16 months, and the 1980 conventions of all three church bodies adopted a two-year study process.
Documents were in the hands of congregational leaders by November of that year, and by 1982 all the pieces were in place for the three churches to have simultaneous conventions so that, on September 8, 1982, with telephone hook-ups so each could hear the others’ votes, all three church bodies voted to proceed on the path toward a new Lutheran church.