Texas spent approximately 10 years as a Republic between 1836 and 1846; a sovereign state straddling the border between Mexico and the United States and bound by controversy. At the time, the Republic encompassed not only all of the current territory occupied by Texas but claims parts of present-day Oklahoma, Kansas, New Mexico, Colorado, and Wyoming. That's a lot of country! Imagine being a north Texan in 1840 and trying to get to South Padre for spring break by the end of the day. Not only was the Republic occupying territory between two dominating powers, but Texas also served as their political and strategic pawn. Dispute over the Republic's southern border, in fact, would ultimately provide the spark that lit up the U.S. war with Mexico. The United States (and the Republic as well) wanted the Rio Grande to serve as Texas' southern border but Mexico, still refusing to enact formal recognition of the Republic's independence, set it at the Nueces River. We all know how it worked out but the interim proved bloody. Santa Ana, Sam Houston's nemesis in the war for independence, rattled his battle saber once again, but Mexico City fell anyway at the hands of General Winfield Scott. The Treaty of Guadalupe Hidalgo wrapped it up for us, including the Rio Grande border for Texas and five new states, including California, for the rest of the country.
Read more about the Mexican War in the Handbook of Texas Online.