My dissertation explores the rise and fall of the vision of “Pacific community” in the decades following the Civil War. It approaches this narrative through the ideas and activities of the “antislavery internationalists” who envisioned connecting the American West and East Asia into a single economic zone. They believed that the transpacific networks of free immigration and free trade would ensure not only their country’s prosperity, but also the vitality of its free labor system in the post-emancipation era. By tracing various figures in the antislavery internationalist circle—Republicans, abolitionists, diplomats and missionaries to China, and intellectuals and journalists advocating free trade—my dissertation argues that free labor ideology, once a weapon used to attack slavery in the American South, was critical in constructing and then destructing the Pacific community. The first section of my dissertation examines the making of the vision of Pacific community, with a special focus on its dual origin in the Whig-Republican tradition of internal improvement and the cosmopolitan worldview of Anglo-American abolitionism. The second section highlights the grassroots challenges to the Pacific community. Analyzing rhetoric of “coolie slave labor” and Chinese “sex slave women,” this section shows that the abolitionist zeal provided rhetorical ammunition to anti-immigration nativists. The last section explores the collapse of the Pacific community, investigating how U.S. restrictions on Chinese immigration closed the Chinese door to American commercial activities in the country. The scholarship of this topic has exhibited periodic, thematic, and disciplinary divisions—between the Reconstruction era and the Gilded Age; the “Chinese question” and the “China question”; and immigration history’s focus on inward-looking nativism and diplomatic history’s emphasis on America’s imperialistic expansion toward the Pacific. Challenging this fragmentation in historiography, my dissertation rediscovers the complex relationships among a set of historical ironies in post-Civil War America: the power of antislavery ideology in the post-slavery era, the collapse of free trade idealism amid Open Door rhetoric, and the rise of Chinese exclusion during the transformation of the United States into a Pacific nation.