English-speaking adults recruit a left-to-right “mental timeline” (MTL) when thinking about time. The origins of the MTL are debated, with some arguing that it is a cultural construct and others arguing it may be innate. Here we ask whether preschoolers, with limited experience with cultural practices thought to shape the MTL, prefer conventional linear representations of events. English-speaking preschoolers and adults were told stories and asked to choose which of two visual representations best illustrated the story. As expected, adults overwhelmingly preferred images that were linearly ordered from left-to-right. Five-year-olds also preferred left-to-right to right-to-left series, but were equally likely choose left-to-right and top-to-bottom. By contrast, 3-year-olds chose at random, apparently insensitive to the spatial ordering of event-denoting images. These results suggest that attention to the ordinal structure of visual representations of time increases across early childhood, and that adults’ preference for horizontal space-time mappings results from increased cultural conditioning.