When Stewart disembarks from the Cannonball at Drucker's store, steam may be seen issuing from the brake hose. Brakes on trains use compressed air, not steam, and even if they did, the valve on the hose would have to be closed or the system wouldn't work.
The sign on the office door of the character played by Bernie Kopell reads "James D. Stewart", however in the closing credits Kopell is billed as "James Stuart".