Since the end of the 17th century, English and French navigators increased their presence throughout the Pacific to connect existing Atlantic trade with Asia. Their navigations through the Pacific familiarized them with advantageous sites—such as in Tierra de Fuego—which functioned as stopovers. These new navigations posed a significant threat to Spain’s attempts to control maritime commerce between the Pacific and Atlantic oceans that passed through American waters. Spain’s need to diversify its maritime routes became clearer still after the Seven Years’ War and the English capture of La Havana and Manila. As a response, peninsular authorities considered extending Spain’s maritime presence in the Pacific by better using isthmus areas like Tehuantepec and Nicaragua. This presentation aims to explain how Spain’s new maritime projects reconsidered the geostrategic position of the isthmus as a crossable point between the Atlantic and the Pacific. In the case of Tehuantepec, the new projects were related to the Maritime Department of San Blas and Spanish expansion into the Northwest of America; in the case of Nicaragua, however, the projects focused on proposals to better connect with Asian trade. These cases let us think about the different particularities that exist in the maritime projects show how Spanish geostrategic considerations for the isthmuses of Tehuantepec and Nicaragua stressed the plurality of imperial visions exerted by late Bourbon officials.