Complex sentence: Texas was annexed by the United States on December 29,1845 and was admitted to the Union as the 28th state on that day, with the transfer of power from the Republic to the new state formally taking place on February 19,1846.
Split into simpler sentences: Texas was annexed by the United States on December 29,1845 and was admitted to the Union as the 28th state on that day. The transfer of power from the Republic to the new state formally took place on February 19,1846.