The Presbyterian Church U.S.A. (PCUSA) embodies the venerable tradition of churches that are “reformed and always being reformed.” The denomination’s modern history reflects this heritage. The PCUSA is the product of three separate bodies that merged over a generation. First, in 1958, the Presbyterian Church in the U.S.A. and the Presbyterian Church of North America joined to form the United Presbyterian Church in the U.S.A., largely a northern denomination. Then, at a historic assembly in Atlanta in 1983, the northern body united with the southern Presbyterian Church of the United States to form the PCUSA.
This three-way union brought together thousands of people with diversity in theology, worship, and social attitudes. This union of three Presbyterian denominations and the pluralism of their members is represented in the three-fold quality of the PCUSA cross and its graphic representation of diversity within unity. The cross also recalls John Calvin's commentary on Paul that "the union ought to be such that we form one body and one soul."
Within the larger design of the PCUSA cross can be found the smaller design of elements held dear by the Reformed and Presbyterian tradition: Word (open Bible on the pulpit) and Sacrament (baptismal font and communion chalice), and the crucial importance of God the Holy Spirit for faithful interpretation (dove and flames). Included also is the ancient symbol of Christian discipleship, the fish (within the body of the dove), and the ancient representation of the Triune nature of God in the general three-in-oneness of the design, as well as in the three-sided triangular base.
Also of interest:
The article A Church Divided by Margaret Shannon provides a contemporary view of the division with Southern Presbyterianism.
Margaret Shannon, “A Church Divided” The Atlanta Journal and Constitution Magazine (28 October 1973, pp. 6-7, 26, 29-30)