In 1964 rapid growth in membership led the church to begin offering two Sunday worship services and church school sessions, with classes for older children relocated to the Harley School to ease crowding. Despite having originally informed Kahn that there would be no need to design the church to accommodate future enlargement, the church trustees decided in September 1964, less than two years after it was completed, to expand the building. Louis Kahn was hired once again as architect, and the addition was completed in May 1969.