Answer:
In 1845, Texas became the 28th state after it was annexed by the United States. Annexation refers to the process by which a territory or region is legally incorporated into another country or state, expanding its boundaries. In the case of Texas, the United States Congress passed a joint resolution to annex Texas, and it was subsequently approved by both the US House of Representatives and Senate. This action officially brought Texas into the Union as the 28th state.