君主  (1791年4月23日～1868年6月1日)

开端 终结 在位 1857年 1861年 

　　詹姆斯·布坎南（James Buchanan，1791年4月23日－1868年6月1日），美国的第十五任总统(1857年3月4日 – 1861年3月4日)。
　　
　　早年生涯
　　
　　詹姆斯·布坎南于1791年4月23日出生于美国宾夕法尼亚州，父母亲来自爱尔兰，布坎南是家中的长子。
　　
　　1807年，布坎南就读于狄更斯学院，攻读法律。1810年又到兰卡士特市跟随詹姆斯·霍金斯学习法律。1812年，布坎南正式成为律师。
　　
　　1814年，布坎南成为兰卡士特郡的郡议员；1815年当选为宾州州议员，担任议员期间他曾大力批评麦迪逊总统、国会和联邦银行，使他得罪了许多人。两届任期后，布坎南在父亲影响下竞选国会议员，但最终落选。
　　
　　1819年，布坎南曾与安妮·柯尔曼订婚，但因为女方父亲反对和人们谣传布坎南已有女友，这项婚约遂告吹。后来女方服药过量而死亡，从此布坎南也终身未婚，成为美国历史上唯一一位单身的总统。后人怀疑因布坎南有同性恋的倾向，而导致安妮悲愤而死。
　　
　　1820年，布坎南代表联邦党当选众议员。其后布坎南转投民主党，被杰克逊总统任命为驻俄公使，在任期间他积极拓展美俄关系。1833年布坎南辞去驻俄大使之职，回国竞选参议员，但不幸落败。1834年，布坎南被递补为参议员，并担任此职达十一年之久。詹姆斯·波特当选总统后，布坎南出任国务卿，期间得克萨斯共和国并入美国，墨西哥政府极为不满，美墨战争遂爆发，以美国取得大胜收场。1848年，布坎南卸任国务卿。
　　
　　总统任内
　　
　　1856年，布坎南获得民主党提名，并当选为第十五任美国总统。
　　
　　由于当时女性意识高涨，女性要求与男性享有同等受教育权利，故布坎南通过了一些保障男女平等的法案。1857年，由于一家人寿保险公司突然宣布破产，触发各地银行的挤兑风潮，全国陷入经济恐慌，但布坎南政府却不采取任何行动，使其政府声望受损。
　　
　　虽然布坎南有为南北和平作出努力，但南北冲突毕竟在他任内激化了。当林肯当选第十六届总统而布坎南尚未卸任时，南卡罗来纳州首先退出联邦，隔一个月又有六个州退出。布坎南对这些州的脱离仍采用怀柔政策，导致全体阁员反对而集体呈辞。当布坎南离开白宫时，民主党已一分为二，十一个允许奴隶制的州发动了叛乱，美国陷入了内战。

　　James Buchanan, Jr. (April 23, 1791 – June 1, 1868) was the 15th President of the United States from 1857–1861 and the last to be born in the 18th century. To date he is the only President from the state of Pennsylvania and the only president to remain a lifelong bachelor.
　　
　　A popular and experienced politician prior to his presidency, Buchanan represented Pennsylvania in the House of Representatives and later the Senate, and served as Secretary of State under President James K. Polk. After turning down an offer for an appointment to the Supreme Court, he served as Minister to the United Kingdom under President Franklin Pierce, in which capacity he helped draft the inflammatory Ostend Manifesto, which suggested the U.S. should declare war if Spain refused to sell Cuba. The Ostend Manifesto was never acted upon and greatly damaged the Pierce administration.
　　
　　Despite unsuccessfully seeking the Democratic presidential nomination several times, Buchanan's nomination in the election of 1856 was a compromise between the two sides of the slavery issue and occurred while he was away on business. His subsequent election was largely due to the even more divided state of the opposition. As President he was a "doughface", a Northerner with Southern sympathies who battled with Stephen A. Douglas for the control of the Democratic Party. Buchanan's efforts to maintain peace between the North and the South alienated both sides, and as the Southern states declared their secession in the prologue to the American Civil War, Buchanan's opinion was that secession was illegal, but that going to war to stop it was also illegal; hence, he remained inactive. By the time he left office, popular opinion had turned against him, and the Democratic Party had split in two. His handling of the crisis preceding the Civil War has led to his consistent ranking by historians as one of the worst Presidents in American history.