Final answer:
The statement that the U.S. Army occupied Mexico City on September 14, 1847 is true, and it was a significant victory in the Mexican-American War, leading to the Treaty of Guadalupe Hidalgo.
Step-by-step explanation:
On September 14, 1847, the U.S. Army, led by General Winfield Scott, successfully occupied Mexico City. This event is true and marked a significant victory for the United States during the Mexican-American War. The capture of Mexico City by the Army of Occupation was part of a three-pronged U.S. military strategy including taking control of northern Mexico and seizing California.
Following the city's fall, the Treaty of Guadalupe Hidalgo was signed in 1848, resulting in Mexico ceding over half its territory to the United States, which included lands that now make up California, Arizona, New Mexico, Nevada, Colorado, Utah, and part of Wyoming.