Much of Nicaragua's politics since independence has been characterized by the rivalry between the liberal elite of León and the conservative elite of Granada. The rivalry often degenerated into civil war, particularly during the 1840s and 1850s. Initially invited by the Liberals in 1855 to join their struggle against the Conservatives, a United States adventurer named William Walker declared himself President in 1856 and made English the official language. (See Walker affair.) Honduras and other Central American countries united to drive him out of Nicaragua in 1857, after which a period of three decades of Conservative rule ensued. They were supported by the United States industrialist Cornelius Vanderbilt, who had originally sponsored Walker in Nicaragua. Walker was executed in neighboring Honduras on September 12, 1860. Three decades of Conservative rule followed.