1493    Christopher Columbus first sights the island now known as Puerto Rico.

1493    Christopher Columbus goes ashore on an island he first saw the day before. He names it San Juan Bautista (later renamed Puerto Rico).

1868    Grito de Lares ("Lares Revolt") occurs in Puerto Rico against Spanish rule.

1873    A law is approved by the Spanish National Assembly in Puerto Rico to abolish slavery.

1898    The United States invasion of Puerto Rico begins with U.S. troops led by General Nelson Miles landing at harbor of Guánica, Puerto Rico (The land invasion, proper, began that day: Sea-based bombardment and shelling of the capital city of San Juan had been occurring since May 1898).

1898    Spanish-American War: American troops enter the city of Mayagüez, Puerto Rico.

1898    United States takes possession of Puerto Rico.

1899    Spain cedes Puerto Rico to the United States.

1900    The Congress passes the Foraker Act, giving Puerto Rico limited self-rule.

1903    El Yunque National Forest in Puerto Rico becomes part of the United States National Forest System as the Luquillo Forest Reserve.

1917    The enactment of the Jones-Shafroth Act grants Puerto Ricans United States citizenship.

1937    Ponce Massacre: 18 people and a 7-year-old girl in Ponce, Puerto Rico, are gunned down by a police squad acting under orders of US-appointed PR Governor, Blanton C. Winship.

1944    A passenger train derails in Aguadilla, Puerto Rico from excessive speed when descending a hill. 16 people are killed and 50 are injured.

1950    Puerto Rican nationalists Griselio Torresola and Oscar Collazo attempt to assassinate US President Harry S. Truman at Blair House.

1952    The U.S. non-incorporated colonial territory of Puerto Rico adopts a "constitution" of local-limited powers, approved by the United States Congress in contravention of then-current international law.

1961    Project Mercury: Mercury-Atlas 5 Mission – Enos, a chimpanzee, is launched into space. The spacecraft orbited the Earth twice and splashed-down off the coast of Puerto Rico.

1963    The Arecibo Observatory in Arecibo, Puerto Rico, with the largest radio telescope ever constructed, officially opens.

2006    The Puerto Rican government closes the Department of Education and 42 other government agencies due to significant shortages in cash flow.

2007    A 7.4 magnitude earthquake occurs off the northern coast of Martinique. This affected the Eastern Caribbean as far north as Puerto Rico and as far south as Trinidad.