Eu recebi uma resposta de Ed Greenwood (um dos autores de Murder in Baldur's Gate e ... sério, você deve saber quem ele é).
Veja o que ele tinha a dizer:
You've got it right: with the established part of Baldur's Gate CRAMMED into the bowl that descends to the river, and with the population of the city growing by leaps and bounds, and with a constant daily need for paddocks, stockyards, caravan assembly and encampment areas, and more warehouses, the part of Baldur's Gate outside the traditional walled area grew...and became the Outer City. It was already happening in the 1360s, but during the Spellplague "time jump," with magic in chaos and therefore "traditional" ways of doing things becoming more important and so more profitable, the growth of "the Gate" grew apace...and the only place it could grow was the Outer City.