American Military History, Volume 1

For two months the only responsible administration in Mexico was the American military government under Scott. The collection of revenues, suppression of disorder, administration of justice, all the details of governing the country were in the hands of the Army. It has been said that some Mexicans believed that Scott's administration of their city was more efficient and respectful of Mexican property than their own government's. It was an instructive lesson in the value of a careful and relatively enlightened occupation policy. When the Mexicans finally organized a government with which Commissioner Trist could negotiate a peace treaty, dispatches arrived from Washington instructing Trist to return to the United States and ordering Scott to resume the war. Knowing that the Mexicans were now sincerely desirous of ending the war and realizing that the government in Washington was unaware of the situation, both Trist and Scott decided to continue the negotiations.

On February 2, 1848, the Treaty of Guadalupe Hidalgo was signed. The U.S. Senate ratified it on March 10, but powerful opposition developed in Mexico. Not until May 30 were ratifications exchanged by the two governments. Preparations began immediately to evacuate American troops from Mexico. On June 12 the occupation troops marched out of Mexico City; on August 1, 1848, the last American soldiers stepped aboard their transports at Vera Cruz and quitted Mexican soil.