The Manufacturers Hanover Trust Building (originally the 600 Fifth Avenue Building), built in 1950-52, was the last addition to the Rockefeller Center complex. Designed by the firm of Carson & Lundin to complement the original Center buildings, the building takes the form of a 28-story tower set on an I-shaped seven-story base. In its scale, materials, ornamental details, and setbacks, the architects created a design which is integral with the Rockefeller Center complex. The first major tenant was the Sinclair Oil Co., and the building was known for many years as the Sinclair Building.