Original: Between 1668 and 1815 , Guam was an important resting stop for the Spanish Manila galleons , a fleet that covered the Pacific trade route between Acapulco ( Mexico ) and Manila ( Philippines ) . Guam , along with the rest of the Mariana and Caroline Islands , were treated as part of Spain 's colony in the Philippines .
Simplified: Spain took over Guam in 1668 , and it was an important place for Spanish delivery boats every year going between Mexico and the Philippines , known as the Manila Galleon .