There shall be firm and universal peace between the United States of America and the Mexican Republic…

Article I, Treaty of Guadalupe Hidalgo, signed February 2, 1848.

The Treaty of Guadalupe Hidalgo was signed in Mexico City on February 2, 1848, ending the Mexican War and extending the boundaries of the United States west to the Pacific Ocean. The terms of the agreement established the border between the U.S. and Mexico at the Rio Grande and the Gila River and granted the U.S. more than 525,000 square miles of former Mexican territory that includes present-day Arizona, California, western Colorado, Nevada, New Mexico, Texas, and Utah. This treaty, along with the 1853 Gadsden Purchase, completed the continental expansion of the United States.

In honor of the 150th anniversary of the treaty signing, the Library of Congress created the online exhibition The Guadalupe Hidalgo Treaty, 1848. It includes page images of the original treaty housed in the Library of Congress Manuscript Division as well as the area map used during the negotiations from the Geography and Map Division.

The Mexican War began with a dispute over the United States annexation of Texas. In January 1846, President James K. Polk, a strong advocate of westward expansion, ordered Zachary Taylor to occupy disputed territory between the Nueces and Rio Grande rivers. Mexican troops attacked Taylor's forces, and Congress approved a declaration of war on Mexico on May 13, 1846. With the capture, by General Winfield Scott, of Mexico City on September 14, 1847, the fighting subsided.

Colonel Lewis Adelbert Norton,
from the Preface to Life and Adventures of
Col. L. A. Norton, 1887.
California As I Saw It: First-Person Narratives, 1849-1900

William T. Sherman caught war fever after hearing of Zachary Taylor's victory at Palo Alto and Resaca de la Palma on May 8, 1846. He soon left his post as a recruiting officer in Pittsburgh and set out for New York, where he boarded a ship bound for California in hopes of joining the fighting. Sherman, who became a famous Union general in the Civil War, describes his journey and experiences of the Mexican War in Part I of his memoir, Recollections of California: 1846-1861.

Lewis Adelbert Norton, a veteran of the Canadian Rebellion of 1837-1839, responded to the declaration of war by raising a volunteer regiment in Kane County, Illinois. He describes his war experiences in Chapters XI through XXIV of his story, Life and Adventures of Col. L.A. Norton. Browse index of Authors in California As I Saw It: First-Person Narratives, 1849-1900 to locate Norton's memoirs of the war.

Search on Mexican War in California As I Saw It: First-Person Narratives, 1849-1900 to locate more recollections of the conflict.

Also, be sure to see the Today in History feature on the Battle of Buena Vista, fought near Monterrey, Mexico in 1847.