The region which now forms the state of Texas had been gradually filling up with settlers.  Many had brought slaves with them, although Mexico abolished slavery in 1829.  The United States tried to purchase the country.  Mexican forces under Santa Anna tried to enforce their jurisdiction in 1836.  Texas declared her independence and drew up a constitution, establishing slavery.  Opposition in the United States to the increase of slave territory defeated a plan for the annexation of this territory.

The New England Anti-Slavery Society was formed 1832, and the American Anti-Slavery Society was founded in Philadelphia in 1833.  William Lloyd Garrison was the leader of abolition as a great moral agitation.

John C. Calhoun, Tyler’s Secretary of State, proposed the annexation of Texas in 1844, but the scheme was rejected by the Senate.  The election of Polk changed the complexion of affairs and Congress admitted Texas, which became a state in December, 1845.

The boundaries had never been settled and war with Mexico followed.  Taylor defeated the Mexican forces at Palo Alto, May 8, 1846, at Resaca de la Palma, May 9th, and later at Monterey and Buena Vista.  Scott was sent to Vera Cruz with an expedition, which fought its way to the City of Mexico by September 14, 1846.  The United States troops also seized New Mexico.  California revolted and joined the United States.  The Gadsden Purchase of 1853 secured a further small strip of territory from Mexico.

The Boundary Treaty with Great Britain, in June, 1846, established the northern limits of Oregon at 49th parallel north latitude.

The plans for converting California into a slave state were frustrated by the discovery of gold.  Fifty thousand emigrants poured in.  The men worked with their own hands, and would not permit slaves to be brought in by their owners.  Five bills, known as the Compromise of 1850, provided that New Mexico should be organised as a territory out of Texas; admitted California as a free state; established Utah as a territory; provided a more rigid fugitive slave law; and abolished slavery in the District of Columbia.

Cuba was regarded as a promising field for the extension of the slave territory when the Democratic Party returned to power in 1853 with the administration of Franklin Pierce.  The ministers to Spain, France and Great Britain met in Belgium, at the President’s direction, and issued the Ostend Manifesto, which declared that the United States would be justified in annexing Cuba, if Spain refused to sell the island.  This Manifesto followed the popular agitation over the Virginius affair.  The Spaniards had seized a ship of that name, which was smuggling arms to the Cubans, and put to death some Americans.  War was averted, and Cuba remained in the control of the Spaniards.

The Supreme Court in 1857, in the Dred Scott decision, held that a slave was not a citizen and had no standing in the law, that Congress had no right to prohibit slavery in the territories, and that the constitution guaranteed slave property.