I recently in another group gave an extensive answer regarding the rise of trains in Equestria. While I did give some lip serve to the idea of them being a cultural import, I mostly focused on them as a native invention. But what better place that this group to consider the alternative? And so I bring the titular question - who created trains? When? And why?

7936564
I think the more pressing matter is why trains are not there anymore. Because theres not much of Equestria anymore. No doubt carted off by flying monkeys by Corporate edict.

G5 folks!

7936564
In my universe the Steam Locomotive was invented in the Kingdom of Albion across the ocean by Earth Ponies in 872 Celestial Reign. In 990 Celestias Reign Etherfuel trains where starting to be used to start phasing out Steam Locomotives. Steam Locomotives wouldn't all be retired until 42 Luna's Return in Equestria. Though Electric and Etherfuel are the majority of trains world wide by 12 Luna's Return.