Final answer:
During the period of dual federalism, the major source of state government power was the state government itself, as dictated by the clear division of authority between state and national governments and reinforced by the U.S. Constitution and Supreme Court rulings.
Step-by-step explanation:
The major source of state government power during the period of dual federalism was (c) State government. During this era, state and national governments exercised exclusive authority in distinctly delineated spheres of jurisdiction. The concept of dual federalism, often compared to a layer cake, highlights the clear division of governing responsibilities between the two levels. This separation meant that state governments had considerable autonomy in managing internal matters.
Under the U.S. Constitution, powers not expressly granted to the national government were reserved for the states. This arrangement was reflective of the context of the period, which favored limited government intervention in the economy and affirmed the states' rights to govern themselves within their jurisdictions. Furthermore, Supreme Court rulings during this time often reinforced the idea of state autonomy by blocking attempts by both the state and federal governments to overstep their constitutional boundaries.