Of the North’s population, over 14.5 million lived in rural areas with a population of less than 2,500, while only 5 million lived in what any reasonable person could call an “urban society.” Roughly 60% of northerners worked on farms. Most farms were small, with the average varying between 113 and 169 acres in the states that stayed loyal to the union. The vast majority of historians and museums have long known these figures and their implications for understanding the war. Why, then, does the state board of education cling to the old story? Perhaps...