Wirelessly posted (BlackBerry8530/5.0.0.601 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)

If it's convenient, the OP can also drop the bags at BAL the day before his departure, and the bags would then be available for pick up at WAS upon his arrival.

My understanding is that if Amtrak offers checked baggage service between two stations, then it must accept checked baggage on the route, regardless of how short the distance between the two stations. A call to Amtrak should confirm this. If the Amtrak baggage agent at BAL balks, speak to the station manager. I had to do that once at BOS when I was traveling on a Regional day train, and wanted to check a bag to NYP. Ultimately, the station manager instructed the baggage agent to accept the bag, and it made it to NYP just fine.