The son of a governor of New Hampshire, Benjamin Pierce, and the former Anna Kendrick, Franklin Pierce attended Bowdoin College in Maine, studied law in Northampton, Massachusetts, and was admitted to the bar in 1827. He married Jane Means Appleton, whose father was president of Bowdoin, in 1834.

Pierce entered political life in New Hampshire as a Democrat, serving in the state legislature (1829–33), the U.S. House of Representatives (1833–37), and the Senate (1837–42). Handsome, affable, charming, and possessed of a certain superficial brilliance, Pierce made many friends in Congress, but his career there was otherwise undistinguished. He was a devoted supporter of President Andrew Jackson (Jackson, Andrew) but was continually overshadowed by older and more prominent men on the national scene. Resigning from the Senate for personal reasons, he returned to Concord, where he resumed his law practice and also served as federal district attorney.

At the time of his election, Pierce, age 47, was the youngest man to have been elected to the presidency. Representing the Eastern element of the Democratic Party, which was inclined for the sake of harmony and business prosperity to oppose antislavery agitation and generally to placate Southern opinion, Pierce tried to promote sectional unity by filling his cabinet with extremists from both sides of the slavery debate. He also attempted to sidestep the fierce sectional antagonisms of the domestic scene by ambitiously and aggressively promoting the extension of U.S. territorial and commercial interests abroad. In an effort to buy the island of Cuba from Spain, he ordered the U.S. minister to Spain, Pierre Soulé, to try to secure the influence of European financiers on the Spanish government. The resulting diplomatic statement, the Ostend Manifesto (October 1854), was interpreted by the American public as a call to wrest Cuba from Spain by force if necessary. The ensuing controversy forced the administration to disclaim responsibility for the document and to recall Soulé. In 1855 an American adventurer, William Walker (Walker, William), conducted a notorious expedition into Central America with the hope of establishing a proslavery government under the control of the United States. In Nicaragua he established himself as military dictator and then as president, and his dubious regime was recognized by the Pierce administration. A more lasting diplomatic achievement came from the expedition that President Millard Fillmore (Fillmore, Millard) had sent to Japan in 1853 under Commodore Matthew C. Perry (Perry, Matthew C). In 1854 Pierce received Perry's report that his expedition had been successful and that U.S. ships would have limited access to Japanese ports. The Pierce administration also reorganized the diplomatic and consular service and created the United States Court of Claims.

Among Pierce's domestic policies were preparations for a transcontinental railroad and the opening of the Northwest for settlement. In 1853, in order to create a southerly route to California, the U.S. minister to Mexico, James Gadsden (Gadsden, James), negotiated the purchase of almost 30,000 square miles of Mexican territory (the Gadsden Purchase), for $10 million. Mainly to stimulate migration to the Northwest and to facilitate the construction of a central route to the Pacific, Pierce signed the Kansas-Nebraska Act in 1854. This measure, which opened two new territories for settlement, included repeal of the Missouri Compromise of 1820 (by which slavery in the territories was prohibited north of latitude 36° 30′) and provided that the status of the territories as “free” or “slave” would be decided by popular sovereignty. The indignation aroused by the act and the resulting period of violent conflict in the Kansas Territory were the main causes of the rise of the Republican Party in the mid-1850s. Owing to his ineptness in handling the situation in Kansas, Pierce was denied renomination by the Democrats, and he remains the only president to be so repudiated by his party. After an extended tour of Europe he retired to Concord. Always a heavy drinker, Pierce descended further into apparent alcoholism, and he died in obscurity.

(For an additional writing by Pierce, see The Military Academy (Franklin Pierce: The Military Academy).)