William Walker, an American adventurer, born in Nashville, Tenn., May 8, 1824, executed at Trujillo, Honduras, Sept. 12, 1860. He studied both law and medicine, was a journalist in New Orleans and San Francisco, and practised law in Marysville, Cal. In July, 1853, he organized an expedition for the conquest of Sonora, but failed for want of supplies, after taking possession of Lower California, and surrendered himself to the United States officials at San Diego. In May, 1854, he was tried at San Francisco for violation of the neutrality laws, and was acquitted. In 1855 some American speculators in Nicaragua induced Walker to interfere in the intestine troubles of that, country, ostensibly in aid of the democratic party. He landed at Realejo on June 11 with 62 followers, was joined by a few natives, fought successfully at Rivas and Virgin bay, took possession of the city of Granada on Oct. 15, and by a treaty with Corral, the opposing leader, was made generalissimo. Corral was tried for treason by a court martial over which Walker presided, and shot Nov. 8. Recruits came from the United States, and on March 1, 1856, Walker had 1,200 men. War breaking out with Costa Rica, he was defeated at Guanacaste on March 20, but had the advantage in a second battle at Rivas on April 11, and hostilities ceased.

He now broke up the interoceanic transit route by confiscating the property and revoking the charter of the Vanderbilt steamship company. In June he caused himself to be elected president, and in September annulled by a decree the existing prohibition of slavery. His arbitrary acts provoked a domestic insurrection, which was seconded by several surrounding states and by agents of the Vanderbilt company; and after a series of battles, on May 1, 1857, he delivered himself up with 16 of his officers to Commander C. H. Davis of the United States sloop of war St. Mary's, by whom he was conveyed to Panama. Thence he went to New Orleans, where he was put under bonds to keep the peace; but in November he was once more in Nicaragua. In December Commodore Paulding, U. S. N., compelled him and his 132 men to surrender, and carried them to New York; but President Buchanan's government declined to recognize Walker as a prisoner, on the ground of the illegality of his arrest on foreign soil. In October, 1858, he sailed with a new expedition from Mobile, in a vessel without a clearance, but was arrested at the mouth of the Mississippi, tried at New Orleans, and acquitted.

In June, 1860, he sailed with a small force from New Orleans to Trujillo, with the design of making a revolution in Honduras. He failed, and was captured and shot. He published " The War in Nicaragua" (Mobile, 1860).