In 1947, the photographer Irving Penn made a black-and-white portrait of a young American musician. He is seated on drab carpeting draped over a chaise-like shape, vaguely old-world. The carpet’s mossy folds throw luxuriant shadows, and the musician upon them wears white tie and tails, a black overcoat caping his shoulders. He is relaxed, his left elbow propped on his left leg, which is hitched up on the seat, and his left cheekbone resting in his left hand as he gazes into the camera. His only visible ear, the right, is large—and as centrally positioned in the portrait as middle C. Is this a fin de siècle poet dressed for the theater? Is that a cigarette butt lying on the floor? Leonard Bernstein never looked more beautiful.

The following year, Penn took a black-and-white photograph of another young American artist, only here the subject is wedged between two walls forming a tight V—a Penn visual trademark. This man, barefoot and wiry, wears a turtleneck and black tights cropped at the calf. His feet press against the walls, a stride that suggests the Colossus of Rhodes. Yet his torso twists in another direction, and his arms are held tightly behind his back, hidden as if handcuffed. His expression is wary. Does the Colossus mistrust the camera or himself? Leave it to Jerome Robbins to choreograph a dance of inner conflict that lasts the length of a shutter’s click.

At this time, most of Penn’s subjects were middle-aged and long-established, but not these two. “Lenny” and “Jerry” were newly minted princes of the city—New York City, the postwar capital of the arts. Both were artists in love with classicism, trained in European traditions yet bending them to their new-world will. And both, in defiance of immigrant fathers who scorned the arts as a losing proposition, had their first big successes at the age of 25.

Each man in his own right was astonishing. Until his death, in 1990, Leonard Bernstein would be the most important musician in America, period. His fourfold eminence as a conductor of the world’s greatest orchestras, a composer of music in myriad forms, a concert pianist, and a teacher on television and at Tanglewood added up to a matchless legacy of accessibility and eloquence, gravity and theatricality, intellectual precision and ecstatic transport. He was a telegenic musical mensch—magisterial. Jerome Robbins, who died in 1998, was less public, a watcher whose uncompromising vision as a choreographer and director—in ballet and on Broadway, in shows filmed and on television—placed the power of dance before America’s baby-boomers and their parents. A storyteller in movement, Robbins daily murdered his darlings and those of his colleagues—dance phrases that were too fancy or distracting, music, text, and emotion that were too much. Truth, moment to moment, was all that mattered. He wasn’t a mensch. He was a perfectionist whose gypsy instinct for the essential, his eye as sharp as a shiv, demanded the best in others or just go home. Few chose to go home. And certainly never Lenny.

Left, Robbins, photographed in his apartment in N.Y.C. by Philippe Halsman, 1959; right, director-choreographer Robbins on the set of West Side Story with Chakiris and Verso. Left, © Philippe Halsman/Magnum Photos; Right, © United Artists/Photofest, Digital Colorization by Lee Ruelle.

Both these men were about energy—positive, negative, generative—and while they racked up stunning achievements separately, they were elevated when joined. Put them together in collaboration—in masterpieces such as the joyous ballet Fancy Free, the breakaway musical On the Town, and the electrifying experiment West Side Story—and you had an ongoing theatrical Manhattan Project, work kinetically detonated, irreducibly true, and oh so American.

They were born within two months of each other, one hundred years ago, in 1918—Louis Bernstein, called “Leonard” by his parents, on August 25 in Lawrence, Massachusetts, and Jerome Wilson Rabinowitz on October 11 in New York City. When they first met, 25 years later, it was the kismet of kindred spirits, their upbringings variations on a theme: middle-class, Russian-Jewish, tough love from difficult fathers who were busy achieving the American Dream. Sam Bernstein did well in his own beauty-supply business, having grabbed the New England franchise for the Frederics permanent-wave machine, a device used in beauty salons, and Harry Rabinowitz, after moving the family to Weehawken, New Jersey, ran the Comfort Corset Company. While both men loved music, including the songs of the synagogue, and took pride in the accomplishments of their children (Lenny had younger siblings Shirley and Burton; Jerry an older sister, Sonia), they expected their sons to come into the family business and were horrified by the artistic ambitions blossoming in their homes. When a piano belonging to Aunt Clara was parked in the Bernstein hallway, Lenny, aged 10, found his reason to be. “I remember touching it,” he said, “and that was it. That was my contract with life, with God. . . . I suddenly felt at the center of a universe I could control.” For Jerry, who’d been playing violin and piano from the age of three and who began taking dance classes in high school, “art seemed like a tunnel to me. At the end of that tunnel I could see light where the world opened up, waiting for me.”