Wikipedia on The Preemption Act of 1841, the Donation Land Claim Act of 1850, and the Homestead Act (1862)
A summary of the Preemption Act
The fight for the Preemption Act
Good summary of the Homestead Act from NARA
Primary Source Document: The Homestead Act
Horace Greeley and the Western Land Debate: “Go West, young man, go forth into the Country.”