Despite the temptation to move their congregations uptown, the three churches with homes north of Washington Square considered it important to maintain a single strong downtown church and chose to merge instead. Charles Parkhurst hoped that “there would be established an institution so securely planted as to be proof against the effect of shifting populations and all other adverse influences that might assert themselves for generations to come.” Each of the three contributed its endowment to the joint project, and each had a particular advantage to offer: Old First provided the best location with its Fifth Avenue address; besides, a recent zoning ordinance that reserved the Avenue south of Fourteenth Street for residential use provided protection. The University Place Church contributed the largest and most active congregation. The Madison Square Church added considerable wealth from the sale of its valuable property. Furnishings were transferred to the Fifth Avenue site as tangible indicators of the union: The pulpit that stands in First Church came from the University Place Church, the baptismal font from Madison Square.
Old First was closed in the summer of 1918 in order to prepare it for its role as the home of the consolidated church. The first service took place on November 3, 1918. In order that it not appear that the identity of any one church was absorbed into that of another, the three pastors, all of retirement age, resigned, Parkhurst from Madison Square, George Alexander from University Place and Howard Duffield from Old First. The new independent First Church would be free to choose its own pastor. It was now a much larger institution, and responsibilities were sensibly divided. Dr. Alexander was chosen as senior pastor, young Thomas Guthrie Speers of Madison Square became an associate pastor responsible for administration, and Harry Emerson Fosdick, a Baptist professor at Union Seminary, would do most of the preaching.
Parkhurst called the new church the “Presbyterian Cathedral of New York City.”