Sadler, one of the leading pioneers of nineteenth-century Texas, participated in most of the major events of the period. He migrated to Texas from Georgia in 1835 to become a farmer. He soon found himself in command of a ranger company that built Fort Houston, served as a private in the battle of San Jacinto, was active in quelling the Cordova Rebellion, and became a leader in the campaign against Chief Bowles and the Cherokees. Eventually he served as a representative in both the Republic Congress and the state legislature. During the Civil War, at the age of sixty-six, Sadler served in Terrell's Texas Cavalry.