“When you look up and see the State House, there is a kind of lightness and grace about it,’’ Dr. Brown told the Globe in 1988, when he retired from the University of Massachusetts at Boston. “I know a good deal about the city and its history, and so when I look at these buildings, in some way, I suppose, figures out of the past come together and blend in with just the plain old visual pleasure of the city.’’

A historian who took as much pleasure in teaching as he did in adding a sure storytelling voice to the history of the Irish in America, he spent 23 years at the university, and previously taught at Notre Dame in Indiana.

Dr. Brown, who was comparatively healthy until his last months, despite heart ailments and a recent bout with respiratory troubles, died Friday in Massachusetts General Hospital. He was 89 and lived in Cambridge.

“I have such esteem for this man,’’ said Pauline Maier, a history professor at MIT who began her career at UMass.

In conversation, in his own writings, and in suggestions scribbled in the margins of manuscripts penned by colleagues and students, Dr. Brown displayed a mastery of the written and spoken word, Maier said.

“This isn’t to be expected among professional historians,’’ she said. “Tom was also a poet. He had a wonderful sense of the subject and a wonderful sense of language. It’s rare that you found someone with those two gifts in the way you found them in abundance in Tom Brown. He was certainly very special.’’

In 1966, Dr. Brown published “Irish-American Nationalism, 1870-1890,’’ and also was a co-writer for the 1998 public television documentary “The Irish in America: Long Journey Home.’’

“He knew more about the Irish in America and about Irish history than anybody else in the United States during his time as an active historian,’’ said Alexander von Hoffman, a former student of Dr. Brown’s and now a senior fellow at Harvard’s Joint Center for Housing Studies.

Dr. Brown was nominated for an Emmy Award, which meant that “essentially, at the age of nearly 79, he was rookie of the year,’’ said his son Chris of Marshfield. “The knowledge he had accumulated through the years found a venue late in life.’’

Although the book and documentary were highly regarded, Dr. Brown’s historical interests were more catholic than simply Irish Catholic. He was fascinated by how ethnic groups would clash, then find ways to cooperate. Too often, he wrote, history books cling to the clashes at the expense of the cooperation. That failing, he said, informs today’s sometimes rocky relations between Boston’s Brahmin Yankees and the Irish, Italian, black, and other minority groups that elbowed their way into the city’s power structure.

“The story of the past is remarkably insistent upon conflict between the various ethnic groups that constitute the citizenry,’’ he wrote in the Globe’s book section in 1985. “Each ethnic group cherishes memories of past conflict and sustains its identity as a group by nursing grievances. Boston’s history is a history of victims.’’

The late J. Anthony Lukas, whose book “Common Ground’’ won a Pulitzer Prize for its piercing look at Boston during desegregation, singled out Dr. Brown as a guiding influence.

“It would be impossible to overestimate the importance of Tom in helping me to understand Boston,’’ he said once in a speech. “In a series of dialogues held at some of the more notorious speakeasies and delicatessens at the base of Beacon Hill, Tom led me through the intricate byways of Boston’s own class and ethnic relationships.’’

Born into a poor family in New York City, Dr. Brown was sent to live with an uncle who ran a resort where boxers trained in New York’s Catskill Mountains.

Dr. Brown attended the College of the Holy Cross in Worcester and enlisted in the Navy in 1940. He was a lieutenant commander and chief engineer aboard destroyers during World War II, and also met Mary E. Slattery, whom he married in 1945.

After a brief stint at the University of Chicago, he finished a bachelor’s degree at Boston College. From Harvard, he received a master’s in 1950 and a doctorate in history in 1956.

Teaching first at Notre Dame, he moved east to join the ranks of the first professors at Boston’s UMass campus, staying until he retired in 1988.

Speaking gently, Dr. Brown infused his lectures with storytelling and engaged his charges in enlightening dialogues.

“He had a breadth of knowledge and a belief that you should always go a little bit further,’’ von Hoffman said.

Dr. Brown’s ancestors hailed from County Cork, which made his chief subject, the Irish in America, as much a part of his soul as his intellect.

“He was fascinated by American history and fascinated by immigrant history,’ said Dr. Brown’s son Dominic of Acton.

His wife, Mary Brown, a chef who ran a French-style restaurant in Watertown, died in 2002.

Dr. Brown worked for many years on a book examining the symbolism of the Bunker Hill Monument, but never finished.

“I often try to position myself so I can view upriver as we pass, to see the old structure of Boston beneath the new one,’’ he told the Globe in 1988. “I love those minutes when I can take in the staggering beauty of the city.’’

In addition to his sons Chris and Dominic, Dr. Brown leaves sons James of Tiverton, R.I., and Nicholas of Holliston; two daughters, Lee of Hancock, N.H., and Margaret of Cambridge; and 11 grandchildren.

A funeral Mass will be said at 10 a.m. today in St. Paul’s Church in Cambridge. Burial will be in St. Joseph’s Cemetery in West Roxbury.