The war between the United States and Spain was caused in some respects by the efforts of Cubans to become independent of Spain and the sympathetic feelings of U. S. citizens.  Also, the Monroe Doctrine of the United States stated that there would be no further interference in the Western Hemisphere by foreign countries without incurring military involvement by the United States, although the intent of the doctrine was also to preserve the status quo. In this case, it was to prevent other countries from attempting to take possession of Spain's New World colonies as they became independent.

After the United States landed troops in Cuba to protect U. S. citizens, a series of events brought relations with Spain to a head, not the least of which was the blowing up of the USS Maine in Havana harbor.  The United States insisted it was a mine, while Spanish inquiries concluded that it was due to an internal explosion, now the prevailing thought.

The results of the war were the independence of Cuba, Puerto Rico becoming a self-governing colony of the United States, and the ceding of the Philippines by Spain to the United States.