Texas sought annexation by the United States.

During the Texas annexation and the Mexican- American war. Also Mexico was not strong enough and american settlers were moving in steadily.
At the Texas Revolution (1835-1836)

Texas was a republic after Texas gained it's Independence from Mexico in 1836, after the revolution, San Jacinto, The Alamo, Goliad, etc. The Republic of Texas gained annexation to the United States in 1845.

in taxas

The importance of the Texas Annexation is that Texas is now a state and Texas still has the power to split itself into four smaller states.