It would depend on the hotel, but many hotels will store it for you. Some will charge, but it's still better than carrying it around all day. Call and ask or ask when checking in.

The museum offers lockers, but they will be a pain as the bags need to be searched first before they can be stored.

Union station has luggage storage, it's near Gate A on the Amtrak concourse and it's supposed to be quite expensive, a previous post said a carry on was $20 for six hours.