Chapultepec (Nahuatl for “Hill of the Grasshopper”), rocky height surmounted by a historic castle, in Mexico City. The terrace of the castle affords a magnificent view of Mexico City. The surrounding area, called Chapultepec Park, contains lakes and fountains, a zoo, an astronomical observatory, stately boulevards, and cypress trees many centuries old.

Chapultepec was known to the early Aztecs as Grasshopper Hill, and the Aztec emperors used the park area for recreation (see Aztec Empire). The hilltop was chosen as the site of the residence of the Spanish viceroy in 1783. Construction of the castle began but was stopped after four years. Although still unfinished, the castle was used as a fortress throughout the colonial period. After years of neglect the castle became the home of the National Military Academy in 1842. The fortifications were modernized shortly before the outbreak of the Mexican War in 1846. Chapultepec Castle was captured by United States troops on September 13, 1847, in the final battle of the war. The victory led to the immediate surrender of Mexico City and the opening of negotiations for a peace settlement.

When Maximilian, emperor of Mexico, made the castle his residence in 1864, the building was remodeled, the interior furnished with imperial splendor, and the grounds beautified. After Maximilian's downfall in 1867, the castle became the summer residence of the presidents of Mexico. In 1937 the property was converted into a national museum and public park. The National Military Academy was subsequently rehoused in part of the castle.

In February and March 1945, during World War II, delegates to the Inter-American Conference on the Problems of War and Peace met at Chapultepec Castle, where they signed the Act of Chapultepec.