With the passing of protective tariff measures in 1816 a readjustment of party lines took place. Protection brought over New England from Federalism to Republicanism. Henry Clay of Kentucky was the leading advocate of protection. Everybody was agreed upon this point in believing that tariff was to benefit all classes. This time was known as "The Era of Good Feeling."
Spain ceded Florida to the United States for $5,000,000.00, throwing in claims in the Northwest, and the United States gave up her claim to Texas. The treaty was signed in 1819.
The Monroe Doctrine was contained in the message that President Monroe sent to Congress December 2, 1823. The colonies of South America had revolted from Spain and had set up republics. The United States recognised them in 1821. Spain called on Europe for assistance. In his message to Congress, Monroe declared, "We could not view any interposition for the purpose of oppressing them, or controlling in any other manner their destiny by any European power, in any other light than as a manifestation of an unfriendly feeling toward the United States....The American Continents are henceforth not to be considered as subjects for future colonisation by any European power." Great Britain had previously suggested to Monroe that she would not support the designs of Spain.
Protective measures were passed in 1824 and 1828. Around Adams and Clay were formed the National-Republican Party, which was joined by the Anti-Masons and other elements to form the Whig Party. Andrew Jackson was the centre of the other faction, which came to be known as the Democratic Party and has had a continuous existence ever since. South Carolina checked the rising tariff for a while by declaring the tariff acts of 1828 and 1832 null and void.
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.