<P> William H. Seward, the former Secretary of State under presidents Abraham Lincoln and Andrew Johnson, had also stressed the importance of building a canal in Honduras, Nicaragua or Panama . He suggested that the United States annex the Dominican Republic and purchase Puerto Rico and Cuba . The U.S. Senate did not approve his annexation proposal, and Spain rejected the U.S. offer of 160 million dollars for Puerto Rico and Cuba . </P> <P> Since 1894, the United States Naval War College had been developing contingency plans for a war with Spain . By 1896, the U.S. Office of Naval Intelligence had prepared a plan that included military operations in Puerto Rican waters . Except for one 1895 plan, which recommended annexation of the island then named Isle of Pines (later renamed as Isla de la Juventud), a recommendation dropped in later planning, plans developed for attacks on Spanish territories were intended as support operations against Spain's forces in and around Cuba . Recent research suggests that the U.S. did consider Puerto Rico valuable as a naval station, and recognized that it and Cuba generated lucrative crops of sugar--a valuable commercial commodity which the United States lacked, before the development of the sugar beet industry in the United States . </P> <P> On July 25, 1898, during the Spanish--American War, the U.S. invaded Puerto Rico with a landing at Guánica . As an outcome of the war, Spain ceded Puerto Rico, along with the Philippines and Guam, then under Spanish sovereignty, to the U.S. under the Treaty of Paris, which went into effect on April 11, 1899 . Spain relinquished sovereignty over Cuba, but did not cede it to the U.S. </P> <P> The United States and Puerto Rico began a long - standing metropolis - colony relationship . In the early 20th century, Puerto Rico was ruled by the military, with officials including the governor appointed by the President of the United States . The Foraker Act of 1900 gave Puerto Rico a certain amount of civilian popular government, including a popularly elected House of Representatives . The upper house and governor were appointed by the United States . </P>

Since when is puerto rico part of the us