Unitarian-Universalism arose from the consolidation of two of the most liberal denominations in North America, and continues to push the boundaries of liberalism, to the point that it is arguably no longer a denomination of Christianity but a small liberal religion unto itself. If we thus bracket out the UUs, who is the genuine liberal edge of North American Christianity? Some would argue for the United Church of Christ (the Congregationalists). An argument can be made for the Episcopalians; and we ought to note the historic vote yesterday of the Evangelical Lutheran Church of America to allow non-celibate gay ministers. Many other answers are also possible, but then again many are not–it’s unlikely anyone would nominate the Southern Baptists or the Missouri Synod Lutherans.
Of course, the answer is somewhat determined by how we choose to define “liberal.” So what do you think: which are the most liberal denominations in North America today? How do you come to that conclusion? Note that while the emphasis here is on Christianity, it may be legitimate to talk about Judaism and other religions as well.