Buck is the duchy where the Royal family traditionally rules from. It is one of the four Coastal Duchies and the home of Buckkeep, the capital of the Six Duchies. Blue is the colour of this duchy, and a charging buck its symbol.
Buck's wealth has two major sources: the rich fishing grounds that the coastal folk have always enjoyed, and the shipping trade created by supplying the Inland Duchies with all they lack via the Buck River. The Buck River is a wide river, meandering freely in its bed, and often flooding the lowlands of Buck during the spring. The current is such that an ice free channel has always remained open in the river year round, save for the four severest winters in Buck's history. Not only Buck goods travel up the river to the Inland Duchies, but trade goods from Rippon and Shoaks duchies, not to mention the more exotic items from the Chalced States and those of the Bingtown Traders. Down the river comes all that the Inland Duchies have to offer, as well as the fine furs and ambers from the Mountain Kingdom trade. - Assassin's Quest