Peace negotiations following the war were begun by the American government in April 1847 after important victories at Buena Vista and Vera Cruz. Nicholas P. Trist was sent as confidential agent with instructions similar to those of Slidell and with full powers to con clude a treaty of peace at a propitious mo ment. In November 1847, however, he received instructions to return. Unexpectedly detained, he finally determined to remain; and without the authority of his government, he negotiated the Treaty of Guadalupe Hidalgo of 2 Feb. 1848, by which the Mexican government ceded New Mexico and Upper California for $15,000, 000 and the American assumption of all Amer ican claims against Mexico. This treaty, in cluding all Polk's sine qua non except the right of transit over Tehuantepec (which had be come less important by the recent acquisition of rights over a better route by the Treaty with New Granada), on its arrival at Washington was hastily accepted by Polk, who, although he refused to pay the salary of the "impudento clerk, was anxious for peace.
For over a quarter-century after 1848, rela tions were disturbed by border turbulence, fili bustering expeditions, Mexican internal trou bles, questions of new claims and of protection of transit routes and apprehension of Euro pean designs or of foreign intervention.
In compliance with a demand for additional territory, James Gadsden concluded with Mex ico a Treaty of 30 Dec. 1853, by which the United States for $10,000,000 obtained south of the Gila River a strip of territory including the Mesilla Valley, and also a right of transit across the Isthmus of Tehuantepec where con flicting interests complicated later negotiations and relations.
The Mexican problem, which thrice had been adjusted by change of boundaries, still per sisted after the Gadsden Purchase. Compli cated with Southern interests, and largely un der the influence of Southern statesmen, the remedy most persistently proposed for its sol ution, in connection with an American transit route across Mexico, was an additional redac tion of Mexican territory by a new cession to the United States, or, if that should fail, the establishment of an American protector& which was expected in time to result in an annexations to the stronger country. The problem, only partially solved by the Pierce administration, was inherited by the Buchanan administration, which continued to negotiate— first, for the acquisition of additional Menial territory and territorial concessions as long as there was any hope of success, and later for territorial concessions and alliance and diner intervention (to enforce treaty stipulations) nil the secession of the Southern States pre cipitated the beginning of the American Ged War and thereby increased the possibility ati probability of the long-predicted intervention of European powers in Mexico. and exposed
Mexican territory to the possible designs 03 Confederate filibusters.
The sequel to the story of persistent Dan ,tiations, which terminated in an unratified treaty, may be found in the Confederate police to form an alliance with Mexico or to absee it, the French policy of intervention in and the American policy under Seward to pre vent the execution of both Confederate and French policies and to preserve the integrc and independence of Mexico.
Through the entire period of the Grill War the American government consistently main tained cordial relations with the constitutiorn! Juarez government. In 1861 it obtained through Mr. Corwin a Treaty of Extradition of Criminals and Fugitives from Justice. To guard against the extinction of the Mexican Republic or the danger of European intend lion, it authorized the negotiation of a troy obligating the United States to pay the inter est on the Mexican funded debt for five yen and to take for security a mortgage or pledgn on the public lands and mineral rights of nori ern Mexico (Lower California, Chihuahua, & flora and Sinaloa). This plan, however, did no meet the approval of France and England aol was also opposed at Washington by senators who feared it might result in annexation.
Against the French invasion and occupatio.7 of Mexico and the establishment of the Mui; milian government, which was regarded inimi cal to republic institutions in America, the government at Washington promptly protested and issued discreet warnings. Later it de manded withdrawal of French forces from Mexico, resulting in the fall of Maximilian in 1867 and the restoration of the republics: form of government.
The United States concluded with Mexico in 1868, a naturalization convention regulating citizenship of emigrants and a claims commis: sion convention for adjustment of nu t= claims. Under the latter a commission was duly organized at Washington 31 July Its powers were extended by convention id 19 April 1871 and again by a convention ci 27 Nov. 1872. A mutual arbitration provided by the treaty gave a balance of about $44T. 000 to American citizens. The famous Pioei Fund Case (q.v.), first presented for adjustmer to the Mexican Claims Convention in 1870. be came a source of a new difference which ire finally settled under a protocol of 1902 submit ting it to the Permanent Court of The Hague.