The Chamorro, of Malay origin, migrated to Guam about 3500 years ago and were there to greet Portuguese explorer Ferdinand Magellan when he sailed into Guam's Umatac Bay back in 1521. Things got off to a bad start when the Chamorro fed and watered Magellan's crew and in return took whatever they could find on the ship. This traditional Chamorro custom of give and take didn't go down well with the Spaniards and before departing, Magellan's crew had killed seven locals and burned 40 houses trying to retrieve a rowboat. Guam and its neighbours were branded Islas de los Ladrones (Islands of Thieves) from then on and the name stuck well into the 20th century.

A new phase in Guam's history began in 1668 when Jesuit priests arrived from Spain on a mission to spread the word. From their base in today's capital of Hagatña, the priests - along with a small Spanish garrison - were well received at first. But as Catholic fervour increased and traditional island hierarchy was eroded, the Chamorro went on the attack. A string of bloody rebellions in the late 1600s, along with outbreaks of influenza and smallpox, saw Chamorro numbers plummet from an estimated 100,000 to about 5000. Most of the survivors were women and children. Spanish soldiers and Filipino men were then bundled in to restock the population, marking the end of the pure Chamorro bloodline.

Following Spain's defeat in the Spanish-American War of 1898, Guam - along with Puerto Rico and the Philippines - was ceded to the USA with the signing of the Treaty of Paris. For the first half of the 20th century, the isaldn was administered by the US Navy except for a brief period beginning in 1941 of 31 months of Japanese occupation during WWII, the only US territory occupied by the Japanese in World War II, when it was taken over for 31 months from 1941. American forces recaptured Guam in 1944.

The Organic Act of 1950 accorded Guam's population with US citizenship and self-government powers, but not the right to vote in national elections. The citizens of Guam went about electing their first governor in 1970, and then two years later headed back to the ballot box to elect their first delegate to the US House of Representatives (albeit a non-voting one). Plebiscites held in 1982 and 1987 indicated that locals were seeking to redefine their relationship with the US, but little has since been achieved on that front.

Today the US presence in Guam is strong, with military facilities dominating the landscape and more than 23,000 military personnel and dependants on the island. Despite years of lobbying to free Guam from its rather blurry 'unincorporated' US territory status, the White House still hasn't bothered to grant the island Commonwealth recognition similar to that of Puerto Rico. Recently-released census information has indicated that about a quarter of the population lives underneath the poverty line.

In April 2002 an earthquake measuring 7.2 on the Richter scale hit the island, followed in July by a typhoon that left many areas without power and running water. In December of that same year the super typhoon Pongsona hit Guam, causing massive property damage which once more brought Guam to its knees. With the help of plenty of Red Cross and FEMA aid, the resilient island has in 2005 all but recovered.