The top 20 laws:
Proclamation Line of 1763: Restricted colonial settlement west of the Appalachian Mountains. Significant because it was the first major attempt to regulate western expansion—and a major source of colonial resentment.
Land Ordinance of 1785: Created the township-and-range survey grid still used today. Structured how western land would be divided, sold, and settled.
Northwest Ordinance of 1787: Established how new western territories would become states; banned slavery north of the Ohio River. Defined the template for all future continental expansion.
Louisiana Purchase (1803): Doubled U.S. territory. Created the geographical foundation for westward expansion and future conflicts over slavery.
Lewis and Clark Expedition Authorization (1803–1804): Not a single statute, but the federal authorization funded the reconnaissance that guided expansion, diplomacy, and claims to the Pacific Northwest.
Indian Removal Act (1830): Authorized removal of Native tribes east of the Mississippi. Central to the forced displacement that opened the Southeast and Midwest to white settlement.
Preemption Act of 1841: Legalized squatter’s rights, allowing settlers to purchase improved land cheaply. Encouraged mass migration into the West before formal surveys.
Texas Annexation Resolutions (1845): Triggered the U.S.–Mexico War; pivotal for acquiring vast southwestern lands.
Oregon Treaty (1846): Secured U.S. claims in the Pacific Northwest. Set the U.S.–British boundary at the 49th parallel.
Treaty of Guadalupe Hidalgo (1848): Ended the Mexican–American War and transferred what is now CA/NV/UT/AZ/NM/CO/WY. The largest land cession in American history after Louisiana.
Homestead Act (1862): Granted 160 acres of free land to settlers. One of the most important settlement laws in U.S. history; dominated western migration patterns for 60 years.
Pacific Railway Acts (1862, 1864): Funded the transcontinental railroad through land grants and loans. Created national markets, population booms, and massive land dispossession for tribes.
Morrill Land-Grant Act (1862): Indirect but major: funded universities that developed agricultural science, transforming the rural frontier economy.
Dawes Act (General Allotment Act, 1887): Dissolved tribal landownership and allotted parcels to individuals. Resulted in the loss of ~90 million acres of Native land.
Reclamation Act (1902): Financed irrigation projects across the West. Enabled settlement of arid regions (CA, AZ, NV, NM); fundamental to modern Western agriculture.
Federal Reserve Act (1913) — Indirect: Created stable capital markets that enabled infrastructure and resource extraction across the West.
Federal Highway Act (1956): The Interstate Highway System made remote regions economically viable. One of the most transformative infrastructure laws for the post-frontier West.
Indian Reorganization Act (1934): Reversed the Dawes Act; restored tribal land bases and governance. Critical for understanding the long arc of federal-Native relations shaped by expansion.
Wilderness Act (1964): Shifted federal land policy from settlement/resource extraction toward preservation. Marked the end of the “expansionist” phase of U.S. land policy.
Alaska Native Claims Settlement Act (ANCSA, 1971): Settled Indigenous land claims in Alaska, transferring 44 million acres to Native corporations. A major modern land-allocation milestone tied to frontier resource extraction.