Final answer:
Organizing history by region focuses on specific areas and their historical developments, while organizing history by period focuses on specific times and their global impact.
Step-by-step explanation:
The main difference between organizing history by region and organizing history by period is the focus of the historian. When organizing by region, a historian looks at a specific area and how historical events and developments have unfolded there. On the other hand, when organizing by period, a historian focuses on a specific time and examines how events and developments have occurred globally or in a broader context.
For example, if a historian is organizing history by region, they might examine the social, political, and cultural changes in Europe during the Renaissance. If they are organizing by period, they might study the global impact of the Industrial Revolution and how it affected various regions around the world.