The idea of manifest destiny encouraged Americans to move west in order to fulfill God's will for U.S. expansion from coast to coast. This expansion was supported by political measures as well. Since its beginning, the United States has grown in size. The map below illustrates the territorial additions of the United States as a result of political decisions over time.

Source: US Territory Map, Perry-Castañeda Library Map Collection

The Northwest Ordinance of 1787 was the political act that supported expansion of the United States to the Pacific. This act, adopted by the Second Continental Congress, established a government for the Northwest Territory. The map below illustrates the Northwest Territory.

Source: Northwest-territory USA 1787, Yassie, Wikimedia

The importance of the Northwest Ordinance was that it provided a method for admitting new states to the Union and provided a bill of rights that were guaranteed in the territory northwest of the Ohio River. This plan of admission was subsequently used in the expansion to the Pacific.

The Northwest Ordinance had the following three main provisions:

• A division of the Northwest Territory into three to five states
• A three-stage method for admitting new states into the Union, including a territorial government
• A bill of rights protecting the same rights of the citizens as those in the 13 colonies

Additionally, the Northwest Ordinance had two other distinctions. Slavery was forbidden within the borders of the territory, and no laws could be enacted if the new law cancelled a previous contract. The Northwest Ordinance was important because it provided the foundation for the creation of later territories within the Union and established the process by which territories became states.

Between 1840 and 1850, the boundaries of the United States changed. In 1840, most of the southwestern corner of the United States was controlled by foreign countries. There was a still a major dispute over the Oregon Country.

By 1850, the United States controlled the land from the Atlantic Coast to the Pacific Coast. This area comprised most of what is the present-day continental United States. Scroll over each outlined area to learn more.

The Compromise of 1850 is another political act that made an impact on the territorial expansion of the United States. The compromise provided five acts that were enacted in September 1850.

The acts included the following:

• Established a boundary between Texas and the United States
• Called for the admission of California as a "free state"
• Provided for a territorial government for Utah and New Mexico
• Called for the abolition of slave trade in Washington, D.C.
• Amended the Fugitive Slave Act, which allowed for runaway slaves to be brought back to their owner