Spain reluctantly agreed to a0 two of its provinces to the united states.

Spain ceded two provinces to the United States as follows:

The initial conflict between the United States and Mexico occurred at the border. In the treaty of 1803 that ceded Louisiana to the United States, Napoleon had transferred the territory that Spain ceded to France in the Treaty of San Idelfonso of 1800. But in that agreement of 1800, Spain simply ceded back to France the province of Louisiana which France had given to Spain in 1762: it consisted of "all that the country knew under the name of Louisiana," without specific frontiers, perhaps because there was no record of the frontiers of Louisiana before 1762. Thus, as Louisiana was transferred from France to Spain (1762), back to France (1800) and then to the United States (1803), its borders were never defined. The US expansion rapidly accelerated at the same time as these negotiations took place, and therefore in 1820, when it seemed that the Spanish government would refuse to ratify the agreement, Jefferson wrote to President Monroe that "I do not regret the non-ratification of the treaty Spanish, "reasoning that" for us the province of Texas will be the richest state in our Union, no doubt. "A gradual flow of US citizens had begun to move to the Mexican state of Texas, even before Spanish ratification of 1821 of the Treaty of Adams-de Onís. Then that year the Spanish commander of the Eastern Interior Provinces of the viceroyalty of New Spain conferred a colonization concession on Moses Austin. Having been ruined by the panic of 1819, Austin planned to rebuild his finances by charging an honorarium to each of the three hundred families he had authorized to settle in Texas. When he died, six months later, the grant passed to his son, Stephen, who in January 1822 established the first legal Anglo-Saxon settlement in Mexican Texas