In a surprise move, Minneapolis Institute of Arts director William Griswold announced Wednesday that he was resigning after just 18 months for a job in New York. Griswold, who presided over the MIA's $50 million expansion and reopening in his brief tenure, is leaving to become director of the posh Morgan Library and Museum on Madison Avenue.

His departure creates the second key leadership void among major Twin Cities arts institutions. Earlier this year, Kathy Halbreich, director of Walker Art Center for 16 years, announced she would leave in November. Griswold and Halbreich had forged a close working relationship, lending art and developing joint programs that helped to defuse a long-simmering rivalry between their institutions.

"I'm surprised, of course," Halbreich said Wednesday. "But then I realized that Bill is in a sense going home because the Morgan is where he really began his career."

Griswold chaired the Morgan's print and drawing department from 1995 to 2001.

Describing the decision as "extremely difficult," Griswold, 46, said he loves the Minneapolis museum and admires its staff and "wonderful" board. "But the opportunity to return to the great institution where I cut my teeth, and for which I have extraordinary affection, was something I couldn't turn down," he said. "I'd spend the rest of my life asking, 'What if?' "

Institute board president Alfred Harrison praised Griswold's era as "a very positive time" for the Minneapolis museum and said "the issue now is can we find a replacement and continue to have superior leadership at the MIA."

A small committee of board members is beginning a director search, hoping to have someone in place by late fall.

Matthew Welch, the institute's curator of Japanese art, said Griswold had been a "fantastic manager" who had restructured the organization, improved staff morale, refined important policies about buying and selling art, and "encouraged us to dream bigger" in planning future shows.

"I want to say I'm devastated, but I'm not because it's not entirely unexpected" that another museum would snap Griswold up, given his talent, enthusiasm and energy, Welch said.

Griswold said he did not go after the Morgan post but was approached by museum board members seeking a successor to Charles Pierce, who is retiring after 20 years. Griswold plans to remain at the Minneapolis museum through January 2008 while the institution seeks a successor.

Opened in 1924, the Morgan is an Italian Renaissance-style palace originally designed to hold the private library and art collection of New York financier Pierpont Morgan. Its 350,000-piece collection includes medieval and Renaissance manuscripts; three Gutenberg Bibles; original scores by Mozart, Beethoven and Bob Dylan; and 5,000-year-old Middle Eastern carvings.

Its Old Master drawings, Griswold's area of expertise, are considered the best in the United States and range from Raphael and Michelangelo to Rembrandt, Rubens, and Cezanne.

The Minneapolis museum and the Morgan are of similar size but different focus. Opened in 1915, the institute is a traditional, broad-based art museum with a staff of 250 and an annual budget of $22 million compared with the Morgan's staff of 130 and $18 million budget. Their endowments are comparable at $164 million in Minneapolis and $160 million at the Morgan.

Both museums finished additions last year. In April the Morgan opened a $106 million expansion by Renzo Piano that unifies its three buildings and adds an auditorium, dining room and enlarged gift shop. In June the institute opened a $50 million addition by Michael Graves. Attendance was 406,000 last year compared with 250,000 at the Morgan.

Director chairs are now empty at 21 American museums, according to the New York-based Association of Art Museum Directors (AAMD). They include plum posts at the National Portrait Gallery in Washington, D.C., the Pennsylvania Academy of the Fine Arts in Philadelphia, the Wadsworth Atheneum in Hartford, Conn., and the Milwaukee Art Museum, among traditional institutions. Along with the Walker Art Center, contemporary museums in Houston and Chicago need directors.

"The Minneapolis Institute is in such great shape that it should be able to attract a really great person," said Mimi Gaudieri, executive director of the AAMD. Having Walker in play also should not be a problem because "they're such different institutions and would attract different kinds of professionals," she said.

Mary Abbe • 612-673-4431 • mabbe@startribune.com