Ever wonder why was it was called the Manhattan Project? Because that is where the top-secret initiative began before it migrated to Los Alamos, N.M., and concluded in Hiroshima and Nagasaki. It could even have been called the Morningside Heights Project, since it was propelled by a pioneering cyclotron at Columbia University. We see a portion of that tubular antique in a show at the New-York Historical Society, just past a vintage Philco radio that once delivered broadcasts like the one we hear of Edward R. Murrow reporting on the Blitz.


This illuminating new exhibition, “WWII & NYC,” even makes it seem plausible that the waging of the entire war was a kind of Manhattan Project, at least in part. We make our way through some 300 objects, ranging from prewar protest pamphlets to postwar artworks, and see, again and again, just how central New York was to the war effort and how powerfully the conflict affected the city’s evolution. New York wasn’t generally on the front lines — though German U-boats sank tankers in local waters — but with its port, manufacturing, ship building and strategic military centers, it made the front lines possible.


This might seem unremarkable, but in this exhibition the society has again taken on a subject that we might overlook, examining it closely through a distinctive lens and transforming our perceptions. The show’s curator, Marci Reaven, the society’s vice president for history exhibitions, has, with few exceptions, cultivated complications and complexities, with an eye for telling details.


New York, from the first, was not united about the war or what should be done about it. We see local traces of pacifism, radicalism, fascism and isolationism — the city could have been a staging ground for the war itself. From 1941, there is an anti-isolationist cartoon by Theodor Seuss Geisel, who became the postwar baby-boomer fantasist Dr. Seuss. There is also a Teutonic poster promoting a German American Bund celebration of Nazi youth culture in 1939 Brooklyn, along with a photograph of festivities at Camp Siegfried on Long Island, where the “Horst Wessel Song” was sung, and rustic paths were named after Hitler and Goering. (Later we learn that the prewar American salute during the Pledge of Allegiance so resembled the Nazi gesture that the hand on the heart became a permanent replacement.)


There are also wartime products here from regional factories that reinvented themselves. We see an M1 carbine, one of the Army’s standard firearms, assembled like hundreds of thousands of others in plants run by I.B.M. The bra manufacturer Maidenform, we learn, had to lobby for its products to be recognized as wartime essentials for the female work force, but it hedged its bets with a “pigeon vest,” shown here and used to cradle homing pigeons behind enemy lines. It “resembles a bra in construction,” the exhibition tells us, “with snug but comfortable mesh to allow the bird to breathe.”


The first penicillin factory in the world, we learn, was opened by Charles Pfizer & Company in Brooklyn in 1943, making 90 percent of the drug carried by Allied forces on D-Day. (Rare samples are on display.) Steinway & Sons in Queens switched from making pianos to fashioning glider wings (presumably because, like piano rims, they required layers of hard wood shaped into set curves).


We also learn that the two ground-floor galleries of the historical society were turned over to the American Red Cross, which produced four million surgical sponges here by December 1944. And the Arms and Armor Department of the Metropolitan Museum of Art designed the helmets and body armor for American soldiers and bomber crews, based on historical models.


But it isn’t just that New York factories and museums were altered. The war had an immense physical presence here. Some 900,000 New Yorkers served in the military; by 1945 about 3.3 million American servicemen had shipped out through “the country’s principal war port.”


One mural shows us silhouettes of tankers, troopships and tugboats in the nocturnal New York Harbor: a convoy of ships, grouped for protection against attack, making its way with troops and supplies across the Atlantic. Between 1942 and 1944, more than one convoy a day left the harbor. In 1943 alone, 488 convoys were dispatched — 7,039 ships. By 1944, New York’s port was handling 50 percent more ship traffic than all other United States ports combined.


A deliberately old-fashioned illuminated display shows us a map of the region, with lights marking military and strategic centers. The Army’s Eastern Defense Command was on Governors Island, responsible for guarding the American coast. On Staten Island an anti-submarine net was laid to protect the harbor, a net constructed, we are informed, by the John A. Roebling’s Sons Company “of Brooklyn Bridge fame.”


The Office of Strategic Services — the forerunner of the C.I.A. — was housed in Rockefeller Center. And the Brooklyn Army Terminal — still an astounding sight on the coastline — was the largest warehouse of its time, unloading and storing freight, and housing the Port of Embarkation command headquarters that coordinated the international movements of American soldiers. (Among the fine videos here is a too-brief tour of World War II harbor sites with the historian Kenneth T. Jackson, a consultant for the exhibition.)