Final answer:
The Homestead Act of 1862 helped settlers by granting them 160 acres of free land provided they lived on and improved the land, thereby playing a crucial role in promoting Western migration and supporting the Civil War effort. Therefore, the correct option is D.
Step-by-step explanation:
The Homestead Act of 1862 played a significant role in assisting settlers in the West by offering them an opportunity to claim 160 acres of federal land. To benefit from the act, settlers had to live on the land for five years and make improvements such as cultivating fields and building homes. This legislation aimed to encourage Western migration, increase agricultural output for the Civil War effort, and extend the 'free soil' mentality across the West to oppose the expansion of slavery.
Among the multiple-choice options provided in the question, the correct answer is D. The Homestead Act offered free land for settlers to encourage them to move west and improve the land. This action was one of the key strategies the U.S. government implemented to assist with and promote the goal of Western expansion during the 19th century.