Republic of Texas–United States relations refers to the historical foreign relations between the now-defunct Republic of Texas and the United States of America. Relations started in 1836 after the Texas Revolution, and ended in 1846 upon the annexation of Texas by the United States.
US involvement in Texan independence 
Following Mexico's independence from the Spanish Empire in 1821, the population of Texas numbered only 4000 Tejano citizens. The new Mexican government, eager to populate the region, invited Americans to help settle the region; by 1830 the number of American settlers in Texas topped 30,000. Slavery was brought to Texas by the settlers even though the 1824 Mexican constitution declared the process illegal; in 1831 the Mexican government began to combat slavery in Texas, intensifying the desire of the Texans to seek independence. By 1835, Sam Houston and other Texans initiated the battle for independence. The United States decided to support the revolution by providing arms and supplies to the Texas rebels, eventually leading to the independence and creation of the Republic of Texas.
Independent Texas shown by Texan Flag
, Mexican territory claimed by Texas shown in Velvet Red.
Bilateral relations 
In 1831 The United States opened an embassy in Austin, in 1841 The Republic of Texas opened an embassy in Washington, DC.
From republic to state 
Relations between Texas and the US were strong; however, Texas had become unstable and unfit to fully defend or sustain itself, prompting the US to consider annexation. Upon annexation, Mexico declared war on the US. The US would later annex New Mexico and Alta California, and Texas would attempt secession as a Confederate state.
See also