Walker, WILLIAM (1824-1860), a famous American adventurer and filibuster, born at Nashville, Tenn. He graduated at the University of Nashville, was admitted to the bar and later studied medicine at Edinburgh and Heidelberg. Returning to America, he engaged in journalism, but in the summer of 1853 he organized an expedition to conquer the State of Sonora, Mex. After capturing several towns and proclaiming himself president, he was forced to flee from Mexico on account of a lack of provisions and ammunition and was arrested by United States authorities at San Diego. He was tried for violating neutrality, but was acquitted. He soon started upon an expedition to Nicaragua, then engaged in a civil war. There he was made secretary of war and commander in chief of the government forces, but quarreled with the president and condemned him to death for conspiracy. Walker then directed a brief and triumphant war with Costa Rica and proclaimed himself president. His arbitrary conduct, however, resulted in his expulsion from the country, and he again surrendered to United States authorities. As soon as possible, however, he returned to Nicaragua with a force of Americans and natives and was again driven from the country. After several attempts he later made an expedition to Honduras, but was compelled to surrender to the Honduran government, was condemned by court martial and executed in 1860.