Why is Sam Houston important to our history?

Republic of Texas Following the Texas Declaration of Independence on March 2, 1836, Houston joined his volunteer army at Gonzales, but was soon forced to retreat in the face of the superior forces of Mexican General (and dictator) Antonio López de Santa Anna, whose soldiers killed all those at The Alamo Mission at the conclusion of the Battle of the Alamo on March 6.
Houston at the Battle of San Jacinto.

The painting "Surrender of Santa Anna" by William Huddle shows the Mexican general Santa Anna surrendering to a wounded Sam Houston.
At the Battle of San Jacinto on April 21, 1836, however, Houston surprised Santa Anna and the Mexican forces during their afternoon siesta. Badly beaten, Santa Anna was forced to sign the Treaty of Velasco, granting Texas independence. Although Houston stayed on briefly for negotiations, he returned to the United States for treatment of a wound to his ankle. Houston was twice elected president of the Republic of Texas (the first time on September 5, 1836). He served from October 22, 1836, to December 10, 1838, and again from December 12, 1841 to December 9, 1844. On December 20, 1837, Houston presided over the convention of Freemasons that formed the Grand Lodge of the Republic of Texas, now the Grand Lodge of Texas. He put down the Cordova Rebellion of 1838, and while he initially sought annexation by the U.S., he dropped that hope during his first term. In his second term, he strove for fiscal prudence, and worked to make peace with the Indians and to avoid war with Mexico, following the two invasions of 1842. He had to act over the Regulator-Moderator War of 1844, which caused him to send in the militia.