The famous theorist behind the Homestead Act of 1862 was President Abraham Lincoln. The act aimed to promote westward expansion by providing 160 acres of public land to settlers for a small fee, provided they improve the land by building a dwelling and cultivating crops. This legislation reflected Lincoln's vision for making land accessible to ordinary Americans, fostering individual opportunity and economic growth. It played a crucial role in settling the western United States, encouraging migration and the establishment of agricultural communities while significantly impacting Native American lands and rights in the process.