What is the earliest documented song about steam trains?

Trains have been a staple of song writing since the 19th Century but what is the earliest documented song about a train?

The question is prompted by listening to this song from 1909, In My Merry Oldsmobile.

No idea, but it did remind me of this:

See

http://www.railserve.com/music/#Railroad Songs

Some stuff from 1830