1845 The Independent Republic of Texas existed from December 19, 1836 through December 28, 1845 and included a part of Wyoming. On December 29, 1845, Texas was admitted into the Union as the 28th state. A part of Wyoming was admitted as Texas on that date. Below is an 1846 map of the Western United States showing the state of Texas. It was published by S. Augustus Mitchell.
The image is courtesy of the David Rumsey Historical Map Collection