Today (Dec. 29th) in 1845, Texas was admitted into the United States as the 28th state.

After gaining independence from Spain in the 1820s, Mexico welcomed foreign settlers to Texas which was sparsely populated at that time. A large group of Americans led by Stephen F. Austin settled along the Brazos River. The Americans soon outnumbered the resident Mexicans, and by the 1830s attempts by the Mexican government to regulate these American communities led to rebellion.

In March 1836, in the midst of armed conflict with the Mexican government during the The Texas Revolution (October 2, 1835 – April 21, 1836), Texas declared its independence from Mexico and became an independent Republic.

After the War, intermittent conflicts between the two countries continued into the 1840s.

Six months after the congress of the Republic of Texas accepts U.S. annexation of the territory, Texas is admitted into the United States as the 28th state on December 29th, 1845.

The state's annexation then set off a chain of events that caused the Mexican–American War in 1846. The Mexican–American War was an armed conflict between the United States of America and the United Mexican States from 1846 to 1848. The 1848 Treaty of Guadalupe Hidalgo ended the war. The United States received the disputed Texas territory, as well as New Mexico territory and California.