Spanning some fifty-four years, The Union on Trial is a fascinating look at the journals that William Barclay Napton (1808-1883), an editor, Missouri lawyer, and state Supreme Court judge, kept from his time as a student at Princeton to his death in Missouri. Although a northerner by birth, Napton, the owner or trustee of forty-six slaves, embraced a proslavery analysis of American society. Focusing on events between the 1850s and 1870s, especially those that led to the Civil War and Reconstruction, The Union on Trial contains Napton's political reflections, offering the important perspective of an educated northern-cum-southern rightist on the key issues that turned Missouri toward the South during the Civil War era. Although Napton's journals offer provocative insights into the process of southernization on the border, their real value lies in their author's often penetrating analysis of the political, legal, and constitutional revolution that the Civil War generated. Yet the most obvious theme that emerges from Napton's journals is the centrality of slavery in Missourians' perceptions of themselves and the nation and, ultimately, in how border states measured their southernness. Napton's impressions of the constitutional crises surrounding the Civil War and Reconstruction offer essential arguments with which to consider the magnitude of the nation's most transforming conflict. A lengthy introduction contextualizes Napton's life and beliefs, assessing his transition from northerner to southerner largely as a product of his political transformation to a proslavery, states' rights Democrat but also as a result of his marriage into a southern family. Napton's tragic Civil War experience was a watershed in his southern evolution, a process that mirrored his state's evolution and, by way of memory and politics, ultimately defined his family and his home region. Students and scholars of American history, Missouri history, and Civil War studies will find this volume to be of great interest.