1838. Inauguration of transatlantic steam navigation.
1839. Dissolution of the Confederacy of Central America.
1840. William Henry Harrison elected President.
1841. John Tyler succeeds to the Presidency after the death of President Harrison.
1842. Final termination of the Seminole War. The Ashburton Treaty between Great Britain and the United States for the settlement of the Northeastern boundary line concluded. Dorr’s Rebellion in Rhode Island.
1844. James K. Polk elected President. Invention of the electric telegraph.
1845. Admission of Florida and Texas into the Union.
1846. Admission of Iowa into the Union. War begins between the United States and Mexico. The Mexicans defeated at Palo Alto and Resaca de la Palma. Surrender of Monterey. Occupation of California and New Mexico by the American forces. Treaty between Great Britain and the United States for the settlement of the Northwestern boundary-line dispute. Discovery of anæsthetics by Doctor Norton.
1847. General Taylor defeats Santa Anna at Buena Vista. Occupation of Vera Cruz. American victories at Pueblo, Contreras, and Churubusco. Storming of Molino del Rey. Storming of Chapultepec and occupation of the City of Mexico.