time that the flag of Puerto Rico was flown on the island. Velez fled to St. Thomas where he lived in exile. Mattei Lluberas went into exile in New York City, joining a group known as the "Puerto Rican Commission". Spanish Charter of Autonomy After four hundred years of colonial rule by the Spanish Empire, Puerto Rico finally received its sovereignty in 1897 through a Carta de Autonomía (Charter of Autonomy). It was signed by Spanish Prime Minister Práxedes Mateo Sagasta and ratified by the Spanish Cortes. Seeking independence from the United States A few months later, the United States claimed ownership of the island as part of the Treaty of Paris of 1898, which concluded the Spanish–American War, which they had won that year. On 19 February 1904, the Union of Puerto Rico party became the first mass party to advocate for independence for Puerto Rico in the form of a sovereign nation. Other "independence parties" were formed in reaction to the colonial status of Puerto Rico with the United States. The Puerto Rican Nationalist Party, founded 17 September 1922, also advocates independence. This party has since held that, by international law, the Spanish had no authority under the Treaty of Paris to cede the island, which was no longer theirs. The Nationalist movement attracted supporters following the repressions by the island government in the Ponce and the Río Piedras massacre. The profits generated by this one-sided arrangement were enormous, as US corporations developed large plantations. Several years after leaving office, in 1913 Charles H. Allen, the first civilian U.S. governor of Puerto Rico, succeeded to the presidency of the American Sugar Refining Company after serving as treasurer. He resigned in 1915, but stayed on the board. The company operated the largest sugar-refining operation in the world and was later renamed as the Domino Sugar company. According to historian Federico Ribes Tovar, Charles Allen leveraged his governorship of Puerto Rico into a controlling interest over the entire Puerto Rican economy through Domino Sugar. American professor and activist Noam Chomsky argued in the late 20th century that, after 1898 "Puerto Rico was turned into a plantation for U.S. agribusiness, later an export platform for taxpayer-subsidized U.S. corporations, and the site of major U.S. military bases and petroleum refineries." By 1930, over 40 percent of all the arable land in Puerto Rico had been converted into sugar plantations owned by Domino