Robert McCormick Adams, the former chief of the Smithsonian Institution who played a critical role in opening new museums and sought to make "confrontation, experimentation and debate" part of the Smithsonian's mandate, died Jan. 27 at a care center in Chula Vista, Calif. He was 91.

His daughter, Megan Adams, said she did not know the specific cause.

Dr. Adams, a tweedy anthropologist and former provost of the University of Chicago, was secretary of the Smithsonian from 1984 to 1994. He succeeded S. Dillon Ripley II, the patrician executive whose 20-year reign transformed a staid grouping of museums into a world-class center of education, amusement and entertainment.

It was an almost impossible legacy to match, and Dr. Adams tried to play down comparisons with Ripley, who socialized with political leaders and philanthropists. As The Washington Post once reported in a profile, Dr. Adams's notion of a "terrific evening" was soup and a sandwich at home.

The story described him as a "tall, rangy and slightly bowlegged man who looks and talks like a cross between Walt Disney and Walter Cronkite. He dresses sloppily by Washington standards, often has a clump of keys hanging from his belt like a janitor and you get the feeling he'd just as soon hop into a Jeep and be off into the desert."

At lunch, he stood in the Smithsonian's cafeteria line like everyone else, a tray in his hands.

During Dr. Adams's tenure, he oversaw the opening of the National Postal Museum, the National Museum of African Art and the Arthur M. Sackler Gallery. Plans were advanced for an annex of the National Air and Space Museum near Washington Dulles International Airport, the National Museum of the American Indian and the National Museum of African American History and Culture; all opened long after his departure.

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The Smithsonian had long been nicknamed "the nation's attic," a place to store and display tends of millions of items ranging from moon rocks to George Washington's false teeth, from the Hope Diamond to first lady Dolley Madison's dancing slippers.

After five years on the job, Dr. Adams caused a stir of discomfort among Smithsonian regents when he suggested a different approach. He pitched an exhibit on inequality featuring "the lives of the homeless on the grates" and what they "carry with them in their packs of shopping bags."

Other proposals by Dr. Adams — an exhibition about people living in hovels on a burning Manila garbage heap, or a display of urban graffiti — were what he considered only "the beginning of what museums can continue to do."

Some exhibits sparked outrage by detailing ugly undercurrents in American history, such as an exhibition about the U.S. Constitution that included a section on Japanese American internment camps during World II.

The Post's Ken Ringle, reviewing a National Museum of American Art exhibit on the settlement of the West, said it reduced "the saga of America's Western pioneers to little more than victimization, disillusion and environmental rape."

The exhibition also received a stinging rebuke from historian and former librarian of Congress Daniel J. Boorstin as "perverse, historically inaccurate, destructive" and "no credit to the Smithsonian."

Perhaps the greatest fallout came in 1994 from a planned exhibit of the Enola Gay, the U.S. military airplane that dropped an atomic bomb on Hiroshima, Japan, in 1945. The exhibit, proposed for the National Air and Space Museum, infuriated veterans groups, politicians and reportedly some Smithsonian regents who said that it portrayed the Japanese as innocent victims of American violence and revenge. (It fell to Dr. Adams's successor, I. Michael Heyman, to smooth over concerns.)

For his part, Dr. Adams saw his leadership as a corrective to a historical lack of cultural diversity in museum administration.

"There is a new awareness now," he told Smithsonian magazine in 1994, describing how he pushed for Native American representatives to be involved in the process of planning for the American Indian museum. "Minorities are concerned with how they're represented. The white-coated curator who can't be questioned is gone. Curators now are working with communities of people who have a real stake in how their ancestors are seen."

Robert McCormick Adams was born in Chicago on July 26, 1926. His father was a tax lawyer and a distant relation of the storied McCormick family that owned the Chicago Tribune and developed the McCormick reaper.

His early life was spent in rebellion from his upper-class background. He lived for a while in a tough part of Chicago. While attending the Massachusetts Institute of Technology, he spent breaks clearing trails in the Rocky Mountains.

After Navy service during World War II, he enrolled at the University of Chicago, dabbled in campus journalism and dropped out to work in a steel mills and a Ford assembly line. A turning point came when Robert Braidwood, a charismatic archaeologist at the university's Oriental Institute, surreptitiously invited him on a dig in northern Iraq.

"I've never known for sure," Dr. Adams quipped to The Post, "but I think he wanted to take along someone who could fix his cars."

His imagination was sparked by probing how civilizations formed. Dr. Adams completed his undergraduate degree in 1947 and received master's and doctoral degrees in anthropology from Chicago in 1952 and 1956, respectively.

He quickly rose through the academic and administrative ranks at his alma mater and performed ample field research over the decades. His book "Heartland of Cities: Surveys of Ancient Settlement and Land Use on the Central Floodplain of the Euphrates" (1981) is regarded as a seminal text in his field.

His wife of 51 years, Ruth Salzman Adams, a former editor of the Bulletin of the Atomic Scientists, died in 2005. Besides their daughter, of San Francisco, survivors include two stepdaughters and three grandchildren.

After leaving the Smithsonian, Dr. Adams was an adjunct faculty member at the University of California at San Diego. Any institution like the Smithsonian, he said, should change leaders after 10 years.