The Mexican-American War began in May, 1846, following a formal Declaration of War by the United States. The issue was the Texas Republic’s request for annexation to the United States, compounded by a dispute over international boundaries. Mexico had never recognized the Lone Star Republic’s independence from Mexican ownership ten years previously, and now vehemently insisted that the boundary was not the Rio Grande, but the Rio Nueces farther north. President James Polk very much wanted Texas for the Union, and California as well. Leaving nothing to chance, he sent naval warships into California waters. The war ended in Mexico City in September 1847, with the United States victorious. The formal treaty to end hostilities was signed February 2, 1848 at Guadalupe Hidalgo, Mexico—granting the future states of California, Nevada, Utah, most of New Mexico and Arizona, and the disputed Texan regions, to American sovereignty for a payment of $15 million dollars in gold and silver.