This article examines how the Korea Advertising Museum in Seoul participates in constructing narratives of past and present in postmillennial South Korea, and how historical advertisements create ambiguities within those narratives. The analysis is inspired by Benjaminian scholarship on collective dreamworlds and on advertisements as dream‐images, while the curatorial choices are situated against, first, the historical‐cultural specificity of advertising in South Korea and, second, the social‐political imaginaries of the mid‐2000s, when the museum was developed and opened. The article details how the Advertising Museum constructs the post‐democratization South Korean present as the dreamed‐of future, by equating historical progress with a triumphant march of technological, political, and aesthetic freedom to advertise. When museumified old advertisements are brought into the present as technologically and aesthetically archaic, they support the hegemonic narrative of progress and arrival. However, the article also shows how the dream‐images of old advertisements are not perfectly contained. Old advertisements still may shock because their collective utopias remain unattainable in the postmillennial present, despite its technological and industrial sophistication and despite it being declared the hoped‐for future.