The last half of the 19th century was marked by the Puerto Rican struggle for sovereignty. A census conducted in 1860 revealed a population of 583,308. Of these, 300,406 (51.5%) were white and 282,775 (48.5%) were persons of color, the latter including people of primarily African heritage, mulattos and mestizos. The majority of the population in Puerto Rico was illiterate (83.7%) and lived in poverty, and the agricultural industry—at the time, the main source of income—was hampered by lack of road infrastructure, adequate tools and equipment, and natural disasters, including hurricanes and droughts. The economy also suffered from increasing tariffs and taxes imposed by the Spanish Crown. Furthermore, Spain had begun to exile or jail any person who called for liberal reforms. The Spanish–American War broke out in 1898, in the aftermath of the explosion of USS "Maine" in Havana harbor. The U.S. defeated Spain by the end of the year, and won control of Puerto Rico in the ensuing peace treaty. In the Foraker Act of 1900, the U.S. Congress established Puerto Rico's status as an unincorporated territory.