18. DIPLOMATIC RELATIONS OF THE UNITED STATES WITH MEXICO. Early relations were largely determined first by the Mississippi question and later by the failure to define the western limits of Louisiana in the treaty of 1803 and consequent friction with Spain after 1805.
The American government viewed with sympathy the Mexican revolutions, beginning in 1810, and later accorded belligerent rights to the revolutionary government which was aided by filibustering expeditions from the United States; but it endeavored to maintain neutrality until 1822 when, after the final ratification of the Florida Treaty with Spain, it recognized Mexico as an independent state whose govern ment promptly opened Texas to American im migration.
At the close of 1822 Jose M. Zozaya was ac credited first Mexican Minister at Washington, but the real beginning of the Mexican legation dates from the arrival of Pablo Obregon in No vember 1824. In March 1825, the American government sent Joel R. Poinsett as Minister to Mexico to recover the prestige lost by delay, but his methods aroused increasing distrust and suspicion which postponed the completion of treaty negotiations and finally led to his recall. After successfully opposing the plans of Mex ico to unite with Colombia for the liberation of Cuba, he negotiated a Treaty of Commerce of July 1826 and another treaty of February 1828, both of which failed in the Mexican Congress after ratification by the American Senate. He hastily concluded a Boundary Treaty of January 1828 which was lost by delay in the Mexican Congress, but was revived in 1832 and ratified following the ratification of the new Treaty of Amity and Commerce negotiated in April 1831 by Anthony Butler, the successor to Poinsett.
Meantime there arose new sources of fric tion which produced strained relations after 1829, temporary severance of relations in 1836 and finally (a decade later) resulted in war. In Texas, which the United States unsuccess fully attempted to purchase in 1825, 1827 and 1829, internal troubles arising from differences between the Mexican government and the American colonists, and increasing after the Mexican attempt to prohibit American immi gration in 1829 and the Mexican establishment of military posts in 1831, finally resulted in a successful revolution of 1835, in which many Americans participated and also in the Amer ican recognition (in 1837) of Texan independ ence — which, together with other grievances, aroused the hostility of Mexico. Relations
temporarily severed in 1836 were again seri ously threatened in 1837 by the withdrawal of the Mexican Minister who was not replaced by a successor at Washington until 1842. In 1835 President Jackson, renewing proposals to Mexico for purchase of Texas, authorized ne gotiations for a boundary on the parallel of 37° westward from the Rio Grande to the Paci fic, but in 1837 he declined Texan offers of an nexation.
Relations were also endangered by Amer ican claims (against Mexico) which in 1837 brought the American government to the verge of reprisals by force. Attempts at adjustment were made by the Convention of 1838 which was not ratified by the American government, and by another Convention which was ratified by both parties in April 1839 and made effective by 'acts of Congress approved on 12 June 1840 and on 1 Sept. 1841. These claims, allowed by a commission under the Convention of 1839 and a later Convention of 1843, were only partially paid, and later negotiations for another Con vention were prevented by war.
Following the American annexation of Texas by joint resolution in March 1845 (after failure of the Senate to ratify an American Texan Treaty of Annexation), Mexico again severed relations and later refused to receive John Slidell whom President Polk sent to Mex ico to re-establish relations and to negotiate for adjustment of claims and for the annexa tion of California which was the chief aim of his Mexican policy. Finally, in the rich pas ture lands of the border territory in dispute be tween the Rio Grande and the Nueces, the clash of rival military forces precipitated war, recog nized as existing by declaration of the Amer.: ican Congress in May 1846.