Graham died Saturday at his home in Hobe Sound, Fla., from complications of Alzheimer's disease, said his son, George.
At the peak of his influence, from the 1960s through the 1980s, Graham was the top man at Chicago's biggest architectural firm, Skidmore, Owings and Merrill, and had the ear of business leaders and politicians.
Besides the Willis (originally Sears) Tower and the Hancock Center, Graham played a major role in designing such landmark structures as the Inland Steel Building.
"He was the Burnham of his generation," said Chicago historian Franz Schulze, referring to the legendary Chicago urban planner Daniel Burnham.
Reviewing the Sears Tower in 1974, the late Chicago Tribune architecture critic Paul Gapp called the skyscraper "a building whose exterior profiles are a bold, vital and exciting departure from orthodox mediocrity."
The 110-story, 1,451-foot Sears Tower reigned as the world's tallest building from 1973 to 1996, when it lost its title to the Petronas Twin Towers in Kuala Lumpur, Malaysia. The Chicago skyscraper, which was renamed last year for a British insurance brokerage, remains the nation's tallest.
Graham designed buildings across the nation and world. Yet his most profound influence came in Chicago.
Born Dec. 1, 1925, in Colombia, Graham was the son of a Canadian-born international banker and a Peruvian mother. He grew up in Puerto Rico. Spanish was his first language.
Graham came to the United States as a student in the 1940s. He served in the U.S. Navy and earned his bachelor in architecture from the University of Pennsylvania in 1948.
Graham did his apprenticeship for Chicago architects Holabird, Root and Burgeeat, then left for the up-and-coming firm of Skidmore, Owings and Merrill, where he had a long-running feud with architect Walter Netsch.
"Bruce Graham is very tough," Netsch told the Tribune in 1981. "Seldom do you find a good guy who is a great architect."
Graham's greatest achievement came in 1970 with the completion of the mixed-use Hancock Center.
Unlike earlier skyscrapers, in which an internal cage of steel carried most of the load, the Hancock's exterior columns, beams and X-shaped braces formed a rigid tube that did most of the heavy lifting. The arrangement was economical, and the X-braces offered an instantly recognizable skyline image, silencing detractors who had likened the Hancock to an oil derrick.
The Sears Tower offered an even taller variation on the tube theme, consisting of nine interlocked tubes. The tower was built for Chicago-based retailer Sears, Roebuck and Co., which originally had wanted a building of just 60 stories.
As time passed, Sears' luster dimmed. The Sears Merchandise Group left the tower in 1992 for Hoffman Estates.
Graham's survivors include three children, George of New York City, Lisa Graham Langlade-Demoyen of Paris, and Mara Graham Dworsky of Altadena, Calif.; his sister, Margaret Graham Lewis of Gibson Island, Md.; and six grandchildren.