The United Provinces of Coahuila and Texas, formed one State, and its Constitution adopted in 1827, contained an article giving freedom to all who should be hereafter born, and prohibiting the introduction of slaves. The work of emancipation was completed by a decree of the Mexican Congress of 15th September, 1829, manumitting every slave in Mexico.
These successive measures not only frustrated the views of the colonists, and discouraged further emigration from the slave States, but greatly irritated and alarmed the whole slavehoiding interest. The future area of slavery had been greatly contracted by the boundary treaty, and the Missouri compromise ; and now that area was to be bounded on the south and east, as well as on the north, by an unlimited area of freedom. Under such circum- stances, American slavery was doomed. The influence of the free States would soon predominate in the general government, and the growing spirit of abolition would not only extend into the south itself, but would in various ways, endanger the security and permanency of slave property. The colonists in Texas were at present too feeble to break the yoke of freedom imposed on them by the Mexican Government. Against that Government, the United States had no pretext for war"; and the treaty of boundary was too recent and too explicit to permit any claim being made to the territory of Texas. But one resource was. left, and that was purchase.
The government as early as the 15th March, 1827, instructed Mr. Poinsett, our Minister in Mexico, that we wished to change the existing boundary, making it begin at the mouth of the Rio del Norte (Rio Grande), thence lip the river to the Rio Puereo, and then with the last river to its source ; thence' North to the Arkansas, and with this to the 42 ^ North Lat. ; and that for this change of boundary we would give one million of dollars. This modest proposal included almost the whole of Texas as at present claimed.