Medieval city building game Trade Nations has enjoyed success on iOS, clocking more than 200 million game sessions in four months and now it’s coming to Facebook with a newly launched port. It is currently ranked as the 17th highest grossing app for iPhones in the U.S. and 14th highest grossing app for iPads after a fresh update.

This title has an interesting backstory. The Facebook version of Trade Nations was developed by Bight Games. But it was originally published on iOS by another studio, Seattle’s Z2Live, which hired Canada’s Bight Games as a contractor to design artwork and gameplay for the title. Both subsequently had a small dispute where they each claimed ownership of the intellectual property behind the game.

But they eventually came to an agreement, with Z2Live telling us that it owns the rights to distribute Trade Nations in perpetuity on iOS while Bight is free to do what they want with the Facebook title.

Trade Nations on Facebook appears to be a faithful port of the iOS game where users build structures in a medieval town and recruit villagers to till the fields, chop the wood, and so on. On iOS, the game is comparable to Ubisoft’s Castle & Co. and Capcom’s Smurfs’ Village; we expect that on Facebook, it will be compared to other medieval life sims like Knight’s Story and to any number of farming and city building sims.

On the monetization side, Trade Nations sells a premium currency called Magic Beans that can be used to accelerate building or purchase special decoration items. On Facebook, Credits is the sole means of acquiring Magic Beans. A standard currency, Coins, is earned by completing in-game tasks.

We’ll have a more in-depth review of Trade Nations for Facebook in the coming weeks as the game grows on our sister site Inside Social Games. You can follow its progress on AppData, our traffic tracking service for social games and developers.

TradeNations becomes yet another in a series of mobile apps that have crossed over to the Facebook platform, following Glu Mobile’s Gun Bros and Pocket God. Rovio Mobile is planning to bring a version of Angry Birds to Facebook in the near future, which the company has been working on for a year. But the poster child for true cross-platform success is still PopCap Games’ Bejeweled Blitz.