I passed the time on a recent flight to Pittsburgh, the City of Bridges, by reading Jackie Robinson's autobiography. I had picked it up because something about Barack Obama's "A More Perfect Union" speech -- about the style in which it was delivered as much as its content -- had put me in mind of the man who, 61 years ago this April, broke the color line in baseball. I thought Mr. Obama's speech was courageous, in Ernest Hemingway's sense of the word; an example of "grace under pressure." And there was something about Mr. Obama on that dais in Philadelphia, a measured, self-possessed and solitary black man with the eyes of the nation upon him, that called to mind an image of Robinson, standing alone against the vast black-and-white roar of Ebbets Field, aware in every nerve and to the marrow of his bones of the importance of his standing there, bearing an unimaginable burden of history, hatred and aspiration.

As I walked the streets of my old hometown of Pittsburgh, past the buildings of the University of Pittsburgh Law School where Forbes Field once stood, my thoughts turned from Robinson to Roberto Clemente, another black man whose integration into the game had engendered similar if less epoch-making tensions. Though he was by no means the first dark-skinned Latino player in the major leagues, Clemente became the first Latino superstar, and like Robinson he shouldered a great weight of expectation each time he stepped onto the field, playing every game for the honor of Puerto Rico, the Hispanic ballplayer and Spanish-speaking Americans everywhere.

If Clemente was never obliged to stand up to the harsh, even bestial treatment that Robinson received, still he was subjected early on to segregated hotels, restaurants and spring training camps. Like Robinson he endured the cruel ethnic baiting and the well-meaning racism of newsmen and fans. And because Clemente's rise to greatness was more gradual than Robinson's, and because he played in the hinterlands, and because he did not have Robinson's heroic air of the lonely pathfinder, "the only black man on the field," as Robinson put it, Clemente never attracted the instant adulation (especially among black fans and the young of all races), that helped make Robinson's ordeal a little more bearable. Isolated by color and by language, he labored under a false reputation for arrogance, aloofness, and an unwillingness to make nice to the media.

As a result of his clutch performances in the World Series of 1960 and 1971, the deftness with which he ran the base paths and ranged the vastness of right field at Forbes, and the air of tragic nobility that surrounds his death, Clemente has also come to embody the idea of grace under pressure, for me and a million other baseball fans, particularly in Pittsburgh, where today he is immortalized with street names and statues and remembered with a pride and affection that tends to pass over the bitterness and hurt that marked so much of Clemente's career.

There may be nothing racist in the way that we leach the anger and the bitterness from the stories of our black heroes, forgetting the outbursts of long-suppressed rage, the sardonic and aggrieved remarks; forgetting the bogus knock on Clemente, fostered by the press, for being ignorant and temperamental; forgetting the persistent rap of Robinson's being a "rabble rouser" and a "sorehead," a slander which resulted directly from Branch Rickey's granting Robinson permission, at long last, not to turn the other cheek.

You could argue that we subject white heroes and heroines to the same kind of treatment, that we prefer our heroes, regardless of race, to be unambiguous, and when a shadow falls across them we take it as a betrayal. But white Americans tend to make the suppression of anger (and the bitterness that its prolonged suppression distills) a greater and more exacting precondition for heroic status in a black man than in anyone else.

I don't hear bitterness or anger when Mr. Obama speaks, or sense it lying at the back of his writing or oratory. Mr. Obama doesn't need a Branch Rickey to lay a cool, restraining hand on his shoulder. Because Jackie Robinson kept his head, fought his lonely battle, played the game so fiercely and so unanswerably, Barack Obama grew up in an America that was measurably different than the one that Robinson inherited.

When those contemporary political equivalents of the bleacher bums shouting epithets at Jackie Robinson and Roberto Clemente went looking for a vein of rage in Barack Obama, they came away disappointed. They had to go looking elsewhere -- in the sermons of the Rev. Jeremiah Wright -- and try to make the case that, as if by the magic of their own fear and intolerance, Rev. Wright's anger and bitterness belonged to Mr. Obama himself.

I saw grace, the grace of Robinson and Clemente, in the way Mr. Obama balanced a steadfast refusal to surrender to anger with an equally staunch refusal to deny or repudiate its enduring legacy, for good and ill, in the history of race in America. There was grace in the intelligence and abandon of Robinson running the bases, in the fatal arc of a Clemente throw to home from deep right field, in the steadiness and candor that Mr. Obama brought to bear in making his difficult speech on race in America.

And there is grace in the fierce survival, down into this time of homogeneity and gentrification, of the Pittsburgh I remember, with its secret language and wildly manifest accent, its hill-and-hollow, mom-and-pop, ethnic crazy-quilt neighborhoods. As much as any other place in the country, Pittsburgh -- Polish, Italian, African, Jewish, Ukrainian, Scots-Irish, Hungarian, Slovenian, Serbian and, more recently, Indian and Chinese, among others -- embodies and, more importantly, preserves, the spirit of "Out of many, one." The neighborhoods are still there, separated from each other by chasms and ridges and rivers; still linked, stitched up, bound together by 446 bridges.

It's in those bridges that the hope and the greatness of Pittsburgh lie. Though they were built to serve the needs of commerce and industry, other fundamental human needs -- for communication, for connection, for free passage through the world -- also drove their construction. As with courage, a beautifully engineered bridge such as Pittsburgh's Smithfield Street Bridge can be defined as grace under pressure, reconciling distances and bearing heavy loads with elegance and steel. Pittsburghers live in their neighborhoods, but they rely on the bridges they have built to teach them how to live together in their city, through a transfer of shared humanity, a mutual reaching toward the opposite shore.

Though there was mistrust and misunderstanding on both sides, and a certain necessary amount of forgetting, with the passage of time Clemente and the city of Pittsburgh built a bridge. They came to honor, respect and even treasure each other. Like the people of Pittsburgh, Barack Obama understands that we live in a Nation of Bridges -- his life and his history are the proof of it. In steel, stone or acts of human daring, that is the grace bestowed on all of us by those who, in spite of the terrible downward pressures of gravity, or bitterness, or fear, build bridges.