Heading Toward Disunion.

Prior to the Civil War, no American faith took a stand on the question of what, if anything, justified secession from the Union. When the war started in 1861, some denominations escaped its divisiveness by virtue of their structure. The Disciples of Christ, for example, were organized around individual congregations with no central authority; thus different congregations could take individual stands without creating denominational dissent. For other faiths, the process was more wrenching.

Presbyterianism.

The Presbyterians had begun dividing as early as 1800. Old School Presbyterians, who emphasized a trained clergy called by elders to specific congregations and gathered into synods for discussion of doctrinal matters, predominated in the South. The New School, which permitted a less educated ministry and a more congregational polity, predominated in New England and the Northwest frontier. Both Old and New Schools had General Assemblies, at which...