Query: Who is thought to have led to calling Tucson 'The Old Pueblo'?
Context: Tucson is commonly known as "The Old Pueblo". While the exact origin of this nickname is uncertain, it is commonly traced back to Mayor R. N. "Bob" Leatherwood. When rail service was established to the city on March 20, 1880, Leatherwood celebrated the fact by sending telegrams to various leaders, including the President of the United States and the Pope, announcing that the "ancient and honorable pueblo" of Tucson was now connected by rail to the outside world.