City marathons have evolved and grown exponentially in type and popularity, in their managerial complexity, and in terms of their financial impact on their host cities and the attraction of corporate sponsors. Most of the research on city marathons has focused on evaluating their broad economic, urban, tourist, social, sporting, and symbolic effects on host cities. However, less attention has been paid to analyzing key strategic decisions that could account for the evolution and growth of specific marathons and their influences on their management and success. This article, which addresses the cases of the Bank of America Chicago Marathon and the Marathon Valencia Trinidad Alfonso, examines those key strategic decisions that have been taken from their inaugural first editions to present and how effective they have been as regards the management and success of both races. Results show that the international success of both events –in terms of sporting participation, performance, and economic impact– is closely related to critical key decisions taken to improve the design and management of the event; the synergies between the political, business and sporting spheres that the organizational leadership of both races has favored their implementation and, as a consequence, the support received from sponsors. This factor has not only provided both races with financial stability, but it has also contributed to improving how both marathons are managed.