Investigating the American Union explores the historical roots of the United States by examining the events that critically affected the country and continue to do so today. The anthology features essays that focus on the time period of 1400 - 1900, from the time of Columbus and the exploration of the oceans through the emergence of the United States as a true nation. The anthology is divided into three parts, in which the readings progress in chronological order according to the overarching topic. In Part I, Foundations, students read about early globalization, imperial connections, emerging frontiers, and declarations of independence. In Part II, Creating the Union, essays examine the framing and ratifying of the U.S. Constitution, topics of unity and divisiveness in a new world, and how the early republic approached the geographic expansion of a new nation and its social and political implications. In the final part, Breaking the Union, Reconstructing a Nation, students read about presidential politics, the war over slavery, economic development, and the aftermath of emancipation. Investigating the American Union features a unique lens through which students can study the United States' unique past, making it an ideal supplemental text for courses in American history. Mark Eifler is an associate professor of history at the University of Portland. He earned his bachelor's, master's, and doctoral degrees in American history with a specialty in the American frontier from the University of California at Berkeley. He is the author of The California Gold Rush: The Stampede that Changed the World.