Appalachian Mountains: The Appalachian Mountains were a major barrier to westward expansion in the early days of the United States. The mountains were difficult to cross, and the few passes that existed were often treacherous. This made it difficult for settlers to move west and develop new land. As a result, the population of the United States was concentrated along the Atlantic coast.
Great Plains: The Great Plains were another major obstacle to westward expansion. The plains were vast and empty, and there were few roads or settlements. This made it difficult for settlers to travel across the plains and reach the Pacific Ocean. As a result, the development of the West was slowed down.
Deserts of the Southwest: The deserts of the Southwest were also a major obstacle to westward expansion. The deserts were hot and dry, and there was little water or vegetation. This made it difficult for settlers to survive in the deserts and reach the Pacific Ocean. As a result, the development of the Southwest was slowed down.
The transportation revolution helped to overcome these geographic obstacles. The development of steamboats, canals, and railroads made it easier for settlers to travel across the mountains, plains, and deserts. This led to a rapid increase in the population of the United States and the development of the West.