The World, the Flesh and the Devil (1959) on Netflix

Plot summary

Ralph Burton inspects coal mines in Pennsylvania. A cave-in traps him underground, and for five days he hears rescuers digging toward him before the work slows and stops, along with the pumps keeping the shaft from flooding. He digs his own way out and finds a world without people, living or dead. Discarded newspapers announce a retaliatory atomic attack and millions fleeing the cities. Tapes at a radio station explain that an unknown country scattered radioactive sodium isotopes into the atmosphere, and that the dust killed everyone it touched before decaying harmlessly. Ralph travels to New York City looking for survivors and finds it deserted. He restores power to a building and settles in with mannequins for company. A scream leads him to Sarah Crandall, a young white woman who has been living in the city and watching him.