December 29: On this day in 1845, six months after the congress of the Republic of Texas accepted U.S. annexation of the territory, Texas was admitted into the United States as the 28th state.
The Republic of Texas (Spanish: República de Texas) was an independent sovereign nation in North America that existed from March 2, 1836, to February 19, 1846. It was bordered by the nation of Mexico to the southwest, the Gulf of Mexico to the southeast, the two US states of Louisiana and Arkansas to the east and northeast, and the United States territories encompassing the current US states of Oklahoma, Kansas, Colorado, Wyoming, and New Mexico to the north and west. The citizens of the republic were known as Texians.
TL;DR Civics 