Using a narrative approach common in historical analyses, this study seeks to discover the role played by factors such as the presence of external (or Marshallian) economies, local institutions, industrial policy and big companies in the formation and expansion of the São Paulo automotive industry cluster. The evidence presented shows how the clustering of the automotive industry around São Paulo to the detriment of other Brazilian regions in the 1940s is explained by the presence of external economies generated from the 1920s. However, the expansion of the cluster was only possible with the application of strategic policies to protect the nascent industry in the 1950s. The associations of local manufacturers campaigned for the application of this type of policy, which had a bearing on the establishment of strict requirements at the national level. The closing of the market forced the establishment of the big brands in the sector which, from the 1960s, acted as hub companies and hierarchized the cluster. In this phase, the role of the associations of local manufacturers consisted of providing advice and training for the autoparts industry.