What year did texas become part of the united states?

It was on December 29, 1845 that Texas became part of the Union as a slave state.  After winning its independence from Mexico, Sam Houston was elected President of Texas.  Later they promoted the idea of joining the United States.  It doesn’t come as a surprise since many of them originally came from the U.S.  Later on the U.S. would go into war with Mexico and gain more territories.