Because at the time, Texas was also a Mexican territory.
The territories of Texas at the time included present-day Texas, as well as some parts (up to 50%) of Oklahoma, Kansas, Colorado and Wyoming.
Further territory for expansion
. Further territory for expansion
Arizona, New Mexico and Indian Territory
No, Texas went directly from independence to statehood.
The Texas territory
The United States annexed Texas.
The United States never had to fight a war to gain control of Texas and other southwest territories, such as the California territory. Texas was annexed in a time of peace in 1845 by the US; however, this provoked anger from the Mexican government which still did not recognize the independence of the Republic of Texas, and claimed it as still their own territory, albeit a "troublesome one." As a result of the US annexation of Texas, the Mexican-American War broke out.
The Northwest territory, the Louisiana territory, the Texas territory, the New Mexico, California, and Oregon territories, and the Florida territory.
Texas Territory
Texas