Marcy returned to public life in 1853 to serve as
United States Secretary of State under President
Franklin Pierce. On June 1 of that year, he issued a circular to American diplomatic agents abroad, recommending that whenever practicable, they should appear in the simple dress of an American citizen. This directive created much discussion in Europe, where diplomats typically wore
court dress. In 1867, Marcy's recommendation was enacted into law by the US Congress. Marcy resolved the
Koszta Affair (1853), related to detention of an unnaturalized American resident by Austria, gaining his freedom. He negotiated the
Gadsden Purchase from Mexico in the Southwest, the last major land acquisition in the
contiguous United States. It added land to what are now the states of New Mexico and Arizona. With a southern route of territory all under United States control, southerners worked to promote a railroad from Texas to San Diego but were not successful. In 1854 Marcy had to deal with the complications growing out of the bombardment of Greytown (now
San Juan de Nicaragua), by the United States warship
Cyane in retaliation for insults offered the American minister by its inhabitants and for their refusal to make restitution for damages to American property. The expedition of
William Walker to Nicaragua, and his assumption of its Presidency, in 1855, further complicated the Central American question. Upon the 1854 seizure by
Spain of the American vessel
Black Warrior, on the ground that this vessel had violated the customs regulations of the port of
Havana, some propagandists in the
United States Congress as well as
Pierre Soulé, the American minister in Spain, seemed to prefer war and make possible the seizure of
Cuba. It was largely due to Marcy's influence that war was averted, Spain restored the confiscated cargo, paid restitution, and remitted the captain's fine. Three American diplomats met to discuss the future of Cuba, but the resulting
Ostend Manifesto was quite unexpected, and Marcy promptly disavowed the document. The
Crimean War led to a diplomatic controversy with
Great Britain because of British recruiting in several American cities, and in May 1856, the papers of the British representative
Sir John Crampton and several consuls were revoked. The following year the British government sent
Sir Francis Napier to Washington to take Crampton's place. A diplomatic disagreement with Britain caused Marcy to reject the
Declaration of Paris of 1856, which would have set the rules of international maritime law. Other affairs that demanded Marcy's attention were a
Canadian tariff reciprocity treaty, Commodore
Matthew C. Perry's negotiations for naval and trade access with Japan, and a British fishery dispute. ==Death==