Final answer:
Westward expansion following the Civil War was driven by Manifest Destiny, the discovery of gold in California, the completion of the Transcontinental Railroad, and the Homestead Act of 1862.
Step-by-step explanation:
Westward expansion following the Civil War was primarily led by several factors. Firstly, the concept of Manifest Destiny, which emphasized the responsibility to conquer and inhabit new territories, encouraged settlers to move westward. Secondly, the discovery of gold in California in 1848 triggered a mass migration of people to the west in search of fortune. Additionally, the completion of the Transcontinental Railroad in 1869 made transportation to the west faster and more accessible. The Homestead Act of 1862 also played a significant role by offering free land to those willing to move west.