Only seen in the queue in portrait form, the backstory given to him by Walt Disney Imagineering and the updated attraction is as follows:
"Barnabas T. Bullion is the founder and president of the Big Thunder Mining Company. The longtime mining magnate comes from a powerful East Coast family and considers gold to be his very birthright by virtue of his oddly appropriate name; in fact, he considers the ultimate gold strike to be his destiny. And that is why he is having so much trouble with Big Thunder Mountain. According to superstitious locals, Big Thunder Mountain is very protective of the gold it holds within, and the unfortunate soul who attempts to mine its riches is destined to fail. And so far that prophecy is coming to pass. The mine has been plagued by mysterious forces and natural disasters ever since. And yet the Big Thunder Mining Co. is still in operation. In fact, Bullion is discovering new veins of gold and digging new shafts every day, offering a closer look at the Big Thunder mining operation than ever before. But a word to the wise for anyone attempting to visit the mountain: watch out for runaway trains."
Letters in the queue also identify him as a member of the Society of Explorers and Adventurers. He bought a drilling machine from fellow member Jason Chandler for his current mining operation, but in light of the recent supernatural happenings, Chandler has been advising him to stop and move onto a more stable site.
Barnabas T. Bullion is a major character in the Big Thunder Mountain comic, with his daughter Abigail Bullion moving to Rainbow Ridge and getting involved in finding out just what's wrong with her father's mining operation.