Where did most of the lowell mill girls live? ?

Company controlled boarding houses is the correct answer.

Explanation:

The young women and farm girls from New England who were recruited to work in textile factories in Lowell during Nineteenth century were called Lowell Girls. Their life was tightly controlled at factories and at boarding houses which were provided by the company. Many of the Lowell girls joined demonstrations against their working conditions.  An account of these protest was published by The Boston Script in 1834.