REA’s Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. United States History: 1841 to 1877 discusses westward expansion, Texas, the Mexican War, the Compromise of 1850, sectional conflict, the Dred Scott Case, the Lincoln-Douglas debates, the Civil War, and Reconstruction.