Clementine

Maria Isabella Boyd's success as a Confederate spy has made her too famous for further espionage work, and now her employment options are slim. Exiled, widowed, and on the brink of poverty...she reluctantly goes to work for the Pinkerton National Detective Agency in Chicago.
Adding insult to injury, her first big assignment is commissioned by the Union Army. In short, a federally sponsored transport dirigible is being violently pursued across the Rockies and Uncle Sam isn't pleased. The Clementine is carrying a top secret load of military essentials--essentials which must be delivered to Louisville, Kentucky, without delay.