Dusty, we were able to take advantage of their two for one rate in March and then cruised the upper Mississippi from St. Louis on the Mississippi Queen in July when they were offering the $99.00 p/p per night. Otherwise we couldn't have justified the cost, but there are two of us.
The American Queen has a few single rooms available at the double occupancy rate but I believe they'll be based and sailing out of New Orleans next summer as part of a city/steamboat combo.
Here's a travel agent who specializes in the steamboat industry and as a matter of fact was an entertainer on the Delta Queen a few years back. She's been having continuing discussions with the company about single rates. If anyone can help you she can.
and check out her website at phyllisdaletravel.com
Hope you can work out something as it's a great experience. Good luck