Despite an acknowledgement that, historically, the relationship between horse racing, women and fashion was important, existing literature provides little detail on the actual clothes that women wore as racegoers. The aim of this article is to add missing depth on the clothing of fashionable women at horse races, focusing on the United States during the inter-war period. In so doing, the discussion extends understandings of the history, and the material culture, of sporting spectatorship more generally. The article also introduces original work on the male spectator and his racegoing wardrobe. Climatic considerations to do with dressing appropriately for the great outdoors are discussed along with other influential factors on spectator dress such as contemporary fashion journalism and photography. The industry supplying fashion consumers was in transition at this time also and New York acquired prominence as a centre for a new mode of sporty, all-American fashion that was termed sportswear. As well as dealing with the clothes and the individuals who wore them, then, the article tells the story of the broader socio-economic conditions of American fashion, sport and sportswear that formed - and informed - their wearing.