Powder River is an outstanding radio series produced by Jerry Robbiins and ColonialRadioTheater.. I've listened to every episode of every season at least three times and absolutely love this series.
To make for a great experience, buy each of the seven seasons, plus Guns of Powder River & Mountains of Gold. Purchasing the full set will cost you less than many audiobooks.
Visit audible.com for further information or buy them all through Amazon.com, as you desire.