If your station has a lounge, and you are traveling in a Roomette or Bedroom, you can store your luggage for free in the lounge. 

For information about Amtrak baggage allowances, visit: https://www.amtrakvacations.com/trip-planning/at-the-station. 

To learn more about at-station baggage services and storage, visit https://www.amtrak.com/onboard/baggage-policy/at-station-baggage-services.html