In step with the abounding vitality of the time, structural engineer Fazlur Rahman Khan (1929 — 1982) ushered in a renaissance in skyscraper construction during the second half of the 20th century. Fazlur Khan was a pragmatic visionary: the series of progressive ideas that he brought forth for efficient high-rise construction in the 1960s and ‘70s were validated in his own work, notably his efficient designs for Chicago’s 100-story John Hancock Center and 110-story Sears Tower (the tallest building in the United States since its completion in 1974). One of the foremost structural engineers of the 20th century, Fazlur Khan epitomized both structural engineering achievement and creative collaborative effort between architect and engineer. Only when architectural design is grounded in structural realities, he believed — thus celebrating architecture's nature as a constructive art, rooted in the earth — can "the resulting aesthetics … have a transcendental value and quality." His ideas for these sky-scraping towers offered more than economic construction and iconic architectural images; they gave people the opportunity to work and live “in the sky.”  Hancock Center residents thrive on the wide expanse of sky and lake before them, the stunning quiet in the heart of the city, and the intimacy with nature at such heights: the rising sun, the moon and stars, the migrating flocks of birds. Fazlur Khan was always clear about the purpose of architecture. His characteristic statement to an editor in 1971, having just been selected Construction's Man of the Year by Engineering News-Record, is commemorated in a plaque in Onterie Center (446 E. Ontario, Chicago): The technical man must not be lost in his own technology. He must be able to appreciate life; and life is art, drama, music, and most importantly, people.