If you had to pick one site in Chicago as the center of the entire city, it would likely be the Michigan Avenue bridge. The north bank is, according to legend, Jean Baptiste Point du Sable built the first Euro-American settlement and trading post in 1789. Fort Dearborn stood roughly on the south bank, and Cyrus McCormick opened his factory on the du Sable site in 1847. Various industrial concerns moved in and out until 1929, when the north bank was cleared in anticipation of a second Wacker Drive, but the Depression scotched that project and the site became a parking lot. The Tribune bought the land in the 1940s, expecting to build radio and TV studios for its WGN stations, but those ended up in Irving Park and the gateway to North Michigan Avenue remained an eyesore through the 1950s.
Equitable Insurance started discussing the possibility of a combined headquarters and investment tower with the Tribune in 1961. The company had started in New York, in the 1870s and had a long–if checkered–architectural history. George Post engineered their first building, which was known for its early passenger elevators, electric lighting, and fireproof iron construction–which burned, spectacularly, in 1912. Burnham & Co. designed a massive block for the company on the same site–an early collaboration between Ernest Graham and Peirce Anderson. At 40 stories, that building was so overscaled that it helped inspire New York’s zoning code, and Equitable was careful when it expanded in the 1950s to develop urban schemes along with new skyscrapers–particularly in Pittsburgh, where it sponsored the decade-long Gateway Center, and in midtown Manhattan, where it built a plaza-centered tower as part of the Avenue of the Americas extension to Rockefeller Center.
For two decades the company’s Chicago branch office was in a renovated Jenney and Mundie Building on La Salle Street, but Jack Oates, the Chicago native who was Equitable’s CEO at the time found the Michigan Avenue site irresistible for its extraordinary visibility. The Tribune agreed to sell the land on the condition that the new development be set back far enough from Michigan Avenue to guarantee their 1925 Tower views of the River, and the two companies agreed to jointly sponsor a 100,000 square foot plaza that would serve as a forecourt to both buildings. Equitable hired SOM to design the tower, which emerged as what Bruce Graham would call “the most sophisticated building this office has ever done.” With no immediate neighbors, the plan developed as a rectangle of 3 x 5 38-foot structural bays with a central core. Those were large but not excessive; engineer Hal Iyengar recalled later, however, that at 35 stories the tower was at the limit of efficiency for a simple structural frame. SOM relied on welded joints throughout to provide stiffness, oversizing the perimeter girders and columns to create more rigid joints. The result was a step toward the tube frame–Fazlur Khan was working on the DeWitt-Chestnut apartment tower at roughly the same time and there’s at least a fuzzy parallel between that project’s pure tube structure and the Equitable’s stiffened perimeter,
It was Equitable’s curtain wall, however, that represented the most immediate advance in SOM’s skyscraper designs for its extensive use of aluminum, which formed the spandrel and column covers as well as the window mullions and sill rails, which held bronze-tinted glass and granite sill panels in place. The precision allowed by aluminum meant that this curtain wall was subtly more precise than those leading up to it in stainless steel–Inland Steel and Harris Bank in particular–and it marked one more turning point in the gradual move to aluminum for all things curtain wall in the 1960s.
Bruce Graham claimed a direct lineage to the city’s expressive skyscraper tradition, and the layering of horizontal and vertical lines here recalls, if abstractly, the woven grids of structure and ornament that he admired in buildings by Sullivan and Holabird & Roche, among others. But he was not above a Mies trick or two, either, spacing the mullions on the structural grid, leaving slightly narrower windows at the edges of each structural bay that add a syncopation and elegant ambiguity between structure and skin.
The building was almost entirely leased even before the structure was finished–in addition to Equitable, the building attracted two of the city’s largest advertising firms, and ALCOA took one floor for its regional branch offices, among others. The plaza, graced by a sinuous stair to the lower riverwalk (now replaced by Foster + Partners glassy, laptop-like Apple Store) and a fountain dedicated to 25 “pioneers” of the city, retained the vista of the Tribune Tower adequately, but has always suffered from its vast scale–despite planting and pavilions that have sought to break it down, the space functions better as a visual corridor than as a public space.
As one of the most visible sites in the city, Equitable’s construction became a daily attraction to the tens of thousands of pedestrians and drivers who passed it each day–leading the Tribune to produce a daily 15-minute recorded program that it broadcast on speakers to the assembled “sidewalk superintendents” who gathered to watch the drama of high steel being assembled there. Jack Brickhouse, WGN’s sports announcer, delivered the “construction play-by-play.”