In the years following independence, the migration of white settlers and the introduction of black slavery into the immense republic were deterred by Texas` unresolved international status and the threat of a new war with Mexico.  U.S. citizens who had considered migration to the new Republic understood that “life and property in the United States was safer” than in an independent Texas.  In the 1840s, global oversupply had also caused a fall in the price of cotton, the country`s main exporter.  The situation has led to a labour shortage, lower tax revenues, high public debt and a reduction in the Texas militia.   President John Tyler, who concluded that Texas should not become a British satellite, proposed annexation. After some sparring, Houston approved the negotiation of an annexation treaty, which was rejected by the U.S. Senate in June 1844. Annexation then became a theme in the presidential elections of 1844; James K. Polk, who supported the annexation, was elected.
Tyler, who felt the need to hurry around the British plans, proposed to obtain annexation by a joint resolution that would offer the State of Texas, under certain conditions, Texas` acceptance of the merger. The United States Congress passed the annexation resolution on February 28, 1845, and Andrew Jackson Donelson went to Texas to lobby for acceptance of the offer. By handing over the treaty discredited by a Bill sponsored by the House of Representatives, the Tyler administration has triggered sectoral hostilities over admission to Texas.  In the presidential elections of 1844, members of the Congress of the Northern and Southern Democrats were both disoriented by local political unrest in their home countries.  Now, the Northern Democrats felt vulnerable to the appeasement of their southern wing by capitulating to Tyler`s slavery extension provisions. On the other hand, The enthusiasm of Manifesto Destiny in the North has put pressure on politicians to immediately integrate Texas into the Union.  When Secretary of State Upshur accelerated the secret negotiations, Mexican diplomats learned that talks were taking place between the United States and Texas. The Mexican Minister of the United States, Juan Almonte, confronted Upshur with these reports and warned him that if Congress sanctioned an annexation treaty, Mexico would sever diplomatic relations and immediately declare war.  Secretary Upshur dodged the accusations and advanced the negotiations.
 Along with Texas diplomats, Upshur secretly complained in favor of U.S. senators` support for the annexation and provided lawmakers with compelling arguments that associate the acquisition of Texas with national security and internal peace. Early in 1844, Upshur was able to assure Texan officials that 40 of the 52 members of the Senate were forced to ratify the Tyler-Texas Treaty, more than the two-thirds majority required to pass it.  Tyler remained silent in his annual address to Congress in December 1843 on the secret treaty, so as not to harm relations with prudent Texan diplomats.  Tyler did everything he could to keep the negotiations secret, and did not publicly refer to his government`s proactive research in Texas.  The Senate and representatives of the representatives gathered in Congress to say that Congress accepted that the territory, which was duly integrated into the Republic of Texas and rightly belongs to the Republic of Texas, could be built in a new state called the State of Texas, with a form of Republican government that must be adopted by the people of that republic. , by Members of the Convention, gathered with the agreement of the existing government, so that the same thing could be admitted as one of the States of the Union. The Missouri Crisis of 1819-1821 exacerbated the commitments of expansionism among the interests of slavery in the country, when the so-called Thomas-Pension drew the parallel of 36-30` which established parallels at 36-30 degrees in the countries of Louisiana Purchase.  While a majority of members of the Southern Congress accepted the exclusion of slavery from most of Louisiana`s purchase, a