Duke Ellington’s “Take the ‘A’ Train” immortalized New York City’s subways at the speed of jazz. Walker Evans’s 35-mm photographs in Many Are Called (first published in book form in 1966) did so at one-fiftieth of a second. Using his Contax camera surreptitiously from between the folds of his topcoat, Evans copped over six hundred photos on the Lexington Avenue and Broadway lines from 1938 to 1941. On the one-hundredth anniversary of the opening of the subway system, Yale University Press in association with the Metropolitan Museum of Art has reissued Evans’s portfolio of subway riders. The book’s eighty-nine pictures are a classic collection of American portraiture.

Walker Evans (1903-75) was one of the giants of twentieth-century American photography. He stood out not only for his craft, but also for the range of his subject matter and the texture of his work. He documented the restless American soul, the impersonalism of American industry, the artistry of the country’s rural buildings and signboards, and the desolation of the Depression-era South. His Let Us Now Praise Famous Men (1941), conceived and executed with James Agee, was a marriage of visual and literary genius that remains unrivaled. Evans’s photographs came to amplify the work of those he admired (Paul Strand, Dorothea Lang, Helen Levitt) and to inspire a generation (among others, Diane Arbus, Lee Friedlander, and Robert Frank). In fact, it was the New York-savvy Levitt who served as his first decoy and focusing point for these pictures. Stationing himself across from Levitt in a subway car one afternoon in 1938, Evans adjusted his range finder and camera speed. From then on he guessed as he focused on his unsuspecting fellow riders. Although he later apologized, half-heartedly, for his voyeurism, Evans described these photographs as a hunt for “true portraiture,” his attempt to capture the un-self-conscious self.

The subway turned out to be an ideal, if challenging, studio. As Evans later told an interviewer, he wanted unposed portraits where “the guard was down” and the mask was off. Taking Honoré Daumier’s Third Class Railway Carriage as his inspiration, and discovering the uncommon in the mundane, Evans displays a straightforward style and democratic eye in these photographs. He was delighted they turned out to be “at once sobering, startling, and obvious: these are the ladies and gentlemen of the jury.”

Yes and no. First, you might be facing the jury today if you decided to attempt what Evans did fifty years ago. Post-9/11, photographing on the subways is discouraged-despite the omnipresence of the transit authority’s own surveillance cameras. More telling, Evans’s variegated jury pales before today’s riders. It takes less than a New York minute on today’s subway (at a cost of $2 to Evans’s token nickel) to ascertain just how much more diverse and “democratic” a melting pot New York has become.

Evans’s pattern here is nearly a template: generally one or two riders, taken straight on, unaware and seldom looking directly into the hidden camera. The subjects range from a banker to a nun, from exhausted workers to theatergoers to a blind accordionist. The scenes are not wide-angle or vertical, just horizontal rectangles with faces. And since no flash was used and Evans’s film was slow by today’s standards, most of the pictures had to be shot when passengers were seated and the train was at a standstill. In other words, this is not a Graham Greene pursuing his protagonists at breakneck speed through the careening cars of the Orient Express. Rather, Evans’s pictures give off a sense of the incandescent light bulbs then in use in the underground, of the thick layers of paint applied over the cars’ woodwork, of heavy overcoats and the riders’ weary desire to have arrived. There emanates from the photos a surprising meditative quality. Evans’s encounter with the transient reveals something unrepeatable and timeless.

Photographed largely in wintertime in a prewar era of conspicuous hats (I counted 110 in the 89 plates), the Evans subjects were anonymous but come off as open and almost plainspoken. They are mercifully unaffected by the televised self-consciousness of our time.

As any New York subway rider knows, the system, and its people, offer splendid, recurrent epiphanies: the colors, the shapes, the smells, the sounds, the sizes, the sheer cascade of light and reflections in the cars. Despite running on tracks and stopping at predestined stations, you are never sure where a trip is going to launch you. Literally and metaphorically, you can’t be certain where the A Train will let you disembark, or to which Xanadu your thoughts will be transported. The only thing your current Metrocard guarantees is that you will be moved-and changed. Evans gives some clue as to why this is still the case.