Which physical feature of the eastern US was the greater barrier to the westward migration of early American settlers?

The Appalachian Mountains served as the greatest barrier to the westward migration of early American settlers in the eastern US. Their rugged terrain and high elevations made travel difficult, limiting access to the fertile lands beyond. Settlers often had to navigate treacherous paths and face harsh weather conditions, which impeded their movement and exploration of the western territories. This natural obstacle significantly influenced settlement patterns and the timing of westward expansion.