Many thought it would never happen, and it might not have, save for the persistence of Susan Davis, former director of public art at the Philadelphia Redevelopment Authority.
"It's a wonderful story," said Sandra A. Horrocks, vice president of communications and development for the Free Library Foundation.
The eight banners are so large - ranging from 18 feet to 28 feet in length - that only the four shortest could be hung in the library's central lobby.
"They are beautiful," Davis said. "They aren't faded or damaged, except for some small water damage. These are the only banners Calder ever designed."
The banners owe their existence to developer Jack Wolgin, who commissioned three signature works in 1975 as part of the Redevelopment Authority's percent-for-art program requirement.
Wolgin, a collector and lover of contemporary art, was completing his $80 million Centre Square project across from City Hall. Art was a mandated part of the development.
Wolgin's lead tenant, the First Pennsylvania Bank, wanted conventional statuary to grace the building.
"The First Pennsylvania people told him, 'We want a general on a horse,' " recalled Robert Weinberg, Wolgin's attorney. "He told them, 'No. You're getting a clothespin.' "
Claes Oldenburg's now-famous Clothespin was erected as part of the project. Wolgin also commissioned a giant steel sculpture by Jean Dubuffet, Milord la Chamarre, to rise from the lower levels of the Centre Square atrium.
And to hang from the atrium ceiling, he enticed Calder to design a set of banners that eventually filled the space with the bold primary colors of the sun and floral garlands and the silvery tints of the moon and starry night.