Steven R. correctly answered that there was a consolidation of the American Unitarian Association and the Universalist Church of America, not a merger. For years the two groups had been courting one another but couldn’t find a legal way to combine: merger would have legally allowed any dissident group (and indeed there were a minority of Unitarians and a somewhat larger minority of Universalists who resisted union) to claim to represent the authentic tradition of either party and acquire its assets. Finally, Raymond Hopkins, a Universalist minister serving a combined Unitarian and Universalist church (and the first Executive Vice President of the UUA), hit upon the scheme for consolidation: under Massachusetts law, two organizations serving identical functions can be consolidated into a new, third organization that legally becomes heir to their titles and assets. How is this not a merger? Well, merger and consolidation are two separate activities with divergent implications in Massachusetts law, and while the difference may seem arcane to many of us, it was serious enough to hold up the creation of Unitarian-Universalism by as much as fifteen years.
Fifteen years might not strike you as significant, but it would have meant that UUism evolved on a very different trajectory. Not only would UUism be about 30% older as a denomination than it is now, it would have come into being just after the end of WWII, in a very different cultural era. The first president would’ve almost certainly have been Unitarian minister Frederick May Eliot, who would’ve taken things a different direction than Dana Greeley, the actual first president of the UUA. The Fellowship Movement would’ve been a UU venture rather than a Unitarian one; the Humiliati would’ve been a UU revitalization group rather than a Universalist one, and so on. What If is always fun, but of course we can’t re-run history.