1791–1868, 15th President of the United States (1857–61), b. near Mercersburg, Pa., grad. Dickinson College, 1809. Buchanan studied law at Lancaster, Pa., and in practice there gained a considerable reputation for his wide learning and brilliant oratory. Thus prepared, he went into state politics, then entered the national scene as Representative (1821–31), and was later minister to Russia (1832–33) and Senator (1834–45). A Federalist early in his career, he was later a conservative mainstay of the Democratic party. He served (1845–49) as Secretary of State under President Polk and, although Polk exercised a strong personal hand in foreign affairs, Buchanan ably seconded his efforts. The quarrel with Great Britain over Oregon was settled peacefully. That with Mexico, which followed the annexation of Texas and the failure of the mission of John Slidell , led to the Mexican War and the Treaty of Guadalupe Hidalgo (1848). Under President Pierce, Buchanan served (1853–56) as minister to…