The United Presbyterian Church in the United States of America (UPCUSA) was the largest branch of Presbyterianism in the United States from May 28, 1958 to 1983. It was formed by the union of the Presbyterian Church in the United States of America (PCUSA), often referred to (inaccurately) as the "Northern" Presbyterian Church, with the United Presbyterian Church of North America (UPCNA), a smaller church of Covenanter-Seceder tradition at a conference in downtown Pittsburgh, Pennsylvania in May 1958. Vigorous ecumenical activity on the part of PCUSA leaders led to this merger, something of a reunion of two long-separated branches of the larger Presbyterian family deriving from the British Isles.