When Christopher Columbus arrived there in 1493, the island was inhabited by the peaceful Arawak Indians, who were being challenged by the warlike Carib Indians. Puerto Rico remained economically undeveloped until 1830, when sugarcane, coffee, and tobacco plantations were gradually developed. After Puerto Ricans began to press for independence, Spain granted the island broad powers of self-government in 1897. But during the Spanish-American War of 1898 American troops invaded the island and Spain ceded it to the U.S. Since then, Puerto Rico has remained an unincorporated U.S. territory. Its people were granted American citizenship under the Jones Act in 1917; were permitted to elect their own governor, beginning in 1948; and now fully administer their internal affairs under a constitution approved by the U.S. Congress in 1952. In spite of broad popular support for the autonomy of the Commonwealth government and a rapidly modernizing industrial society, there were expressions of dissatisfaction. Puerto Rican extremists dramatized their desire for independence with an attempt to assassinate President Truman on Nov. 1, 1950, and on March 1, 1954, they wounded five congressmen in an attack on the U.S. Capitol.