Best known as Abraham Lincoln’s secretary of state during the Civil War, William Henry Seward conducted full careers as a statesman, politician, and visionary of America’s future, both before and after that traumatic conflict. His greatest legacy, however, lay in his service as the secretary of state, leading the diplomatic effort to prevent European intervention in the conflict. His success in that effort marked the margin between the salvation and the destruction of the Union. Beyond his role as diplomat, Seward’s signature qualities of energy, optimism, ambition, and opportunism enabled him to assume a role in the Lincoln administration extending well beyond his diplomatic role as the secretary of state. Those same qualities secured a close working relationship with the president as Seward overcame a rocky first few weeks in office to become Lincoln’s confidant and sounding board. Seward’s career in politics stretched from the 1830s until 1869. Through that time, he maintained a vision of a United States of America built on opportunity and free labor, powered by government’s active role in internal improvement and education. He foresaw a nation fated to expand across the continent and overseas, with expansion occurring peacefully as a result of American industrial and economic strength and its model of government. During his second term as secretary of state, under the Johnson administration, Seward attempted a series of territorial acquisitions in the Caribbean, the Pacific, and on the North American continent. The state of the post-war nation and its fractious politics precluded success in most of these attempts, but Seward was successful in negotiating and securing Congressional ratification of the purchase of Alaska in 1867. In addition, Seward pursued a series of policies establishing paths followed later by US diplomats, including the open door in China and the acquisition of Hawaii and US naval bases in the Caribbean.