Houston was the guy who led the Texan troops into the Battle of San Jacinto, at which the Texas Revolution was effectively won; Santa Anna was captured there, and when the soldiers brought him to Houston (who was sitting under a tree, having been shot) he took the opportunity to lay out the terms of the peace treaty that would be signed several weeks later. He later became the president of Texas, and the governor of Texas, and a senator from Texas. During his public service in Texas he was a leading advocate of union with the United States--he supported the republic's annexation, and later opposed the state's secession. His political life ended because he wouldn't agree to serve as governor in the Confederacy.
Another notable aspect of the situation is that Houston had already had a perfectly full and eventful life before he ever set foot in Texas, having run away to live with the Cherokees as a teenager, fought in the war of 1812 under Andrew Jackson, taught in a one-room schoolhouse in Tennessee, been elected governor of that state, abandoned the governorship in distress after a catastrophic marriage, and defected to the Arkansas territory, where he lived in a wigwam, was known as The Raven, gave an interview to Alexis de Tocqueville, and spent most of the time drunk. Among other things.
He wasn't a saint but he got a lot done. He was erratic, determined, and ferocious like a child. He careened from disaster to triumph and back again and back again. He burned a lot of bridges along the way, including at San Jacinto, where he ordered the Texans to burn the bridges leading to the battlefield so neither side could retreat. Sometimes he went to bat for an unworthy cause. At other times the cause couldn't have been better and Houston was nearly alone in defending in it. He was very flawed, but also a great person, and a study in the way that a person's virtues and flaws are often the same thing.
Philosophers fall into three major camps about what it means to be good. The consequentialist view is that you're good if you create good results. The deontological view is that you're good if you follow the rules of ethics. The virtue-ethics view is that goodness is individuated; it can only be assessed with reference to the character in question. In the effort to mandate clarity, the consequentialists and deontologists create standards under which the occasional failure is almost inevitable, and any success may be nothing more than luck. The virtue-ethics approach encourages confusion and relativism, and it makes a joke of things like accountability and sin. That's why I think it's the best approach, except for priests or lawyers. People are mutable and complicated. We fall short and let each other down, except when we don't. In giving each other room to run we recognize that people are capable of being both free and good, which is either true or a very honorable lie.