<P> In 1845 , the Republic of Texas was annexed to the United States of America , becoming the 28th U.S. state . Border disputes between the new state and Mexico , which had never recognized Texas independence and still considered the area a renegade Mexican state , led to the Mexican -- American War ( 1846 -- 1848 ) . When the war concluded , Mexico relinquished its claim on Texas , as well as other regions in what is now the southwestern United States . Texas ' annexation as a state that tolerated slavery had caused tension in the United States among slave states and those that did not allow slavery . The tension was partially defused with the Compromise of 1850 , in which Texas ceded some of its territory to the federal government to become non-slave - owning areas but gained El Paso . </P>
<P> In 1845 , the Republic of Texas was annexed to the United States of America , becoming the 28th U.S. state . Border disputes between the new state and Mexico , which had never recognized Texas independence and still considered the area a renegade Mexican state , led to the Mexican -- American War ( 1846 -- 1848 ) . When the war concluded , Mexico relinquished its claim on Texas , as well as other regions in what is now the southwestern United States . Texas ' annexation as a state that tolerated slavery had caused tension in the United States among slave states and those that did not allow slavery . The tension was partially defused with the Compromise of 1850 , in which Texas ceded some of its territory to the federal government to become non-slave - owning areas but gained El Paso . </P>
when did texas become part of the us
when did texas become part of the us
1845
1845