Growing up in evangelical churches, I often heard about some other branch of Christianity called “mainline,” but I never really knew what that meant. I just knew that “mainline” meant “bad” for some reason. It was a little like the word “communist.” I didn’t really know anything about communism, but I heard the word used a lot and knew that communists must be really evil people bent on destroying everything good and beautiful in the world.
But what does “mainline” actually mean? At the simplest level, “mainline” just means that you belong to one of the eight mainline denominations: American Baptist, Christian Church (Disciples of Christ), Episcopal Church, Evangelical Lutheran Church in America, Presbyterian Church (USA), Reformed Church in America, United Church of Christ, United Methodist Church. Sometimes people include other denominations, but these are the eight most common ones.
This isn’t terribly helpful, though. Now we’re left wondering what a makes a denomination “mainline.” So, to figure out more precisely what it means to be a mainline Protestant, we’ll have to figure out what “mainline” itself means. And that’s a trickier proposition because we have several mistaken ideas about the term.