Ysrael Seinuk

Look up as you walk the streets of New York City, and you can appreciate the work of Ysrael Seinuk. As a structural engineer, he is the man who makes tall buildings stand, responsible for the steel-and-concrete core that rises dozens of stories above the earth. In a career that has spanned almost five decades, Seinuk, 73, has plenty of high-profile Manhattan high-rises to his credit, including Philip Johnson's famous "lipstick" building; Trump World Tower, which holds the title of tallest residential skyscraper in the western hemisphere; and Norman Foster's angular Hearst Tower, now under construction.

A pioneering force in the complex world of tall-building engineering, Seinuk was an early proponent of using stronger concrete in New York, a feature that has allowed subsequent generations of engineers to go higher without having to go wider. "My work," says Seinuk, "has always been about stretching the horizon." When he arrived in the U.S. from Cuba soon after Castro's revolution, Seinuk had little more than $20 in his pocket, "my slide rule and my diploma from the University of Havana." The memory of those lean years keeps him committed to a variety of causes in his adopted hometown of New York City and beyond—from cerebral-palsy research to Cuban-American political efforts. "I came to a country that welcomed me," he says. "I make an effort to give back."