This long poem about Texas Jack is from the 1890 book May-Day Dreams, Passion Flowers, Poetic Flights and Prosy Thoughts by Sam Brown Jr., "the Cowboy Poet of the Platte."
Reading this one, a couple of lines stuck with me. "He was all that any maiden might wish for in the shape of man. Half cowboy and half scout, he seemed a youthful errant knight. Poor Texas Jack, how pure thy spirit was! The world hath judged, yet known thee not—hath called thee "wild," "inebriate." A mirthful, bold, but reckless scout, yet, oh, what melancholy and heartache were thine! How tirelessly upon thy track care, despair, and sorrow ever trod."