During World War II, President Roosevelt instituted a Good Neighbor policy aimed at maintaining Allied support among the Latin American nations. At the same time, in Manhattan, Sixth Avenue stood poised for massive postwar rebuilding following the dismantling of the elevated railway. Property owners wanted the city to change Sixth Avenue’s name, to lend the thoroughfare a little class, in the way Fourth Avenue had become Park Avenue.

Mayor La Guardia figured he could kill two birds with one stone. Both to lend symbolic support to the Good Neighbor efforts of his friend in the White House, and to placate property owners, the mayor in 1945 renamed Sixth Avenue as the Avenue of the Americas.

As the Midtown section of the avenue was rebuilt, it emerged as the ultimate corporate corridor. The office buildings, some among the largest in the world, housed some of the country’s largest corporations – including Exxon, the biggest of them all. More than that, the architecture seemed calculated not merely to impress, but to frighten. In the 1950s New York became known as “Headquarters City,” with at times 100 more Fortune 500 headquarters than we have today. Nowhere more than on the Avenue of the Americas could one find a greater symbolic projection of the sheer power of the new global corporations.

The heart of the avenue comprises the “Rockefeller Center Extension.” On the west side of the avenue between 47th and 51st Streets stand four behemoths that were additions to Rockefeller Center, several of the original 1930s buildings of which back onto the east side of the avenue.

Between 50th and 51st rises the Time & Life Building of 1957-9, by Harrison & Abramovitz. This is among the handful of postwar buildings to have received landmark designation. The same architects later added the three buildings, each occupying a full block front, between 47th and 50th. Wallace Harrison himself dubbed these three seemingly identical buildings the “XYZ Buildings.”

The one between 47th and 48th was called the Celanese Building when it opened in 1973. (The avenue once had the headquarters of Celanese, J.P. Stevens, and Burlington. Might we call this the Microfiber Mile?) Next north is the McGraw-Hill Building (1967-73). Between 49th and 50th stands the former Exxon Building (1967-71).

Each of the XYZ Buildings stands back from the avenue behind a large plaza, two of them of the sunken variety that would soon be discredited by the urbanistic studies of William H. Whyte. Each building rises sheer in a scaleless mass that announces, above all, that it is large. Indeed, each comprises nearly 2 million square feet of floor area.

The Time & Life, by contrast, has its quirky charms. Gone is Alexander Girard’s exuberantly Latin-themed restaurant, La Fonda del Sol. Still in place are Harrison’s Rio de Janeiro inspired plaza pavement and lobby floor, with undulating patterns of dark gray and white terrazzo.

Staring at these buildings, one may think that New York, though not the most populous city in the world, may be the heaviest.