this is what i found The Republic of Texas was a short-lived country in North America between the United States and Mexico that existed from 1836 to 1845. Formed as a break-away republic from Mexico as a result of the Texas Revolution, the nation claimed borders that encompassed an area that included all of the present U.S. state of Texas, as well as parts of present-day New Mexico, Oklahoma, Kansas, Colorado, and Wyoming. The eastern boundary with the United States was defined by the Adams-Onis Treaty between the United States and Spain in 1819. Its southern and western-most boundary with Mexico was under dispute throughout the lifetime of the Republic, with Texas claiming that the boundary was the Rio Grande and Mexico claiming the Nueces River as the boundary. This dispute would later become a trigger for the Mexican-American War after the annexation of Texas.