There's a certain place in the retelling of American Unitarian organizational history where the American Unitarian Association is revealed to have once been just an individual membership organization and not a fellowship of churches. (Indeed, I think the last of the life members died in the 1990s.)
Each church is located within the geographical boundaries of one of 16 Associations (14 in Wales and 2 in England). Associations meet several times annually, traditionally every quarter, but now less often in many instances. Strictly speaking, they are not Associations of churches but of Congregationalists within that area, since they do not usually represent the churches nor detract from the independence of the churches.