Lieutenant Teófilo Marxuach (Retired as a Lieutenant Colonel), a native of Arroyo, Puerto Rico, fired the first shot in what is considered to be the first shot of World War I fired by the regular armed forces of the United States against any ship flying the colors of the Central Powers Marxuach, who was a member of the "Porto Rico Regiment of Infantry" and Officer of the Day, on March 25, 1915, opened fire on the Odenwald, an armed German supply vessel, when it was trying to force its way out of San Juan's bay.
In 1919, Félix Rigau Carrera, "El Aguila de Sabana Grande" (The Eagle from Sabana Grande), the first Puerto Rican pilot, became the first native Puerto Rican to fly an aircraft in the island when he flew his Curtiss JN-4 from Las Casas.
Captains Amezquita and Andre Botello decided to put a stop to the destruction and led 200 men in an attack against the enemy's front and rear guard.
They drove Enrico and his men from their trenches and into the ocean in their haste to reach their ships.
It was named after the Province of Caceres in Spain, the birthplace of Nicolás de Ovando, then the Governor of Spain's Caribbean territories, Today it is part of the Pueblo Viejo sector of Guaynabo, just to the west of the present San Juan metropolitan area.
A year later, the settlement was moved to a site then called Puerto Rico, Spanish for "rich port" or "good port", after its similar geographical features to the town of Puerto Rico of Gran Canaria in the Canary Islands.
Artillery from San Juan's fort, El Morro, repelled Drake; however, Clifford managed to land troops and lay siege to the city.
After a few months of English occupation, Clifford was forced to abandon the siege when his troops began to suffer from exhaustion and sickness.
The British attack in 1797, during the French Revolutionary Wars, led by Sir Ralph Abercromby (who had just conquered Trinidad).
His army laid siege to the city but was forced to withdraw in defeat as the Puerto Rican defenses proved more resilient than those of Trinidad.
The population of the Metropolitan Statistical Area, including San Juan and the municipalities of Bayamón, Guaynabo, Cataño, Canóvanas, Caguas, Toa Alta, Toa Baja, Carolina and Trujillo Alto, is about 2 million inhabitants; thus, about half the population of Puerto Rico now lives and works in this area.
San Juan is also a principal city of the San Juan-Caguas-Fajardo Combined Statistical Area.
Various events and circumstances, including liberalized commerce with Spain, the opening of the island to immigrants as a direct result of the Royal Decree of Graces of 1815, and the colonial revolutions, led to an expansion of San Juan and other Puerto Rican settlements in the late 18th and early 19th century.