Fishing boats were not the only ones to cross the Vieques Passage, but also ocean-going ships. In fact, the expanse of water between Isla Cabras and Vieques had become an important passway during the long duration of the Spanish
colonial rule in
Puerto Rico. So, when in 1869 Madrid approved the lighthouse's construction on Isla Cabras, few questioned its wisdom. The initiative was not an isolated event, but part of an island-wide modernization project for "maritime illumination" (es: "Plan de Alumbrado Maritimo en la Isla de Puerto Rico"). Puerto Rico's coasts were coming into the light with the establishment of fourteen lighthouses of which the Isla Cabras Light was the twelfth in line. Though the increasingly liberal local government showed signs of life and interest in developing the island's infrastructure, the overstretched
Spanish Empire, embroiled in wars for independence in
Cuba and the
Philippines, neglected the construction of the Isla Cabras Light. Soon after replacing the Puerto Rican autonomous government with a military regime, the U.S. picked up the light project as part of its naval expansion in the
Caribbean area. In 1904, the
U.S. Coast Guard purchased the of land for $200, and by May 13, 1908, the lighthouse was ready for service. The cost of the undertaking, including the entrance road and the pier, reached a total of $5654.55. ==Structure==