Given the early illustration and historical context of the town of Lowell, the most logical reason for Francis Lowell's partners to choose the area to build the factory town would be:
A river ran through the location and could be used to power the factories.
The use of river water to power the mills was a critical factor in the establishment of many early industrial towns, including Lowell, Massachusetts. Water power from the Merrimack River was harnessed to operate the textile mills, which were central to the town's economy and were one of the defining features of the American Industrial Revolution.