This chapter examines the complex evolution of US–Russian relations during the mid-19th century, highlighting a unique period marked by diplomatic engagement and technological collaboration. In the years preceding the American Civil War, both nations experienced mutual support, particularly as Russia backed the Union during the Civil War. While the popular “common foe” narrative attributes this friendship primarily to shared opposition to Great Britain, a more nuanced perspective reveals the significance of diplomatic interactions and technological exchanges in shaping their partnership. Key figures such as Alexander Bodisco and Thomas H. Seymour fostered goodwill, while Russia’s efforts to modernize its military infrastructure through American expertise solidified practical cooperation. The chapter further explores how territorial expansion in the United States aligned with Russia’s ambitions, and how debates over slavery and serfdom prompted comparative reflections on governance. Despite ideological differences, practical needs and mutual interests facilitated rapprochement, culminating in strengthened ties during the Civil War and setting the stage for future interactions.