The Lowell System was the first example of major factories in the United States. The system employed mostly young women in large factories making textiles.
Before the Lowell System took hold, most commercial textile production had been done via the "putting-out" system. In this system, raw materials would be given out to individuals who would work on them in their own homes. For example, thread might be given out to a number of individuals who would weave the thread into cloth in their own homes (men wove cloth, but weaving became a woman's job too). They would then bring the finished product to the owners who had given them the thread.
The Lowell System moved towards a modern manufacturing system. Instead of putting out thread or other raw material, the Lowell System had all of the work done in one place. This was the beginning of industrialization in the US.
The Lowell System was a plan developed in the early 19th century to promote and expand textile manufacturing. Textile mills relied heavily on a labor force of women and children. It expanded the idea of the factory system. It was all part of the Industrial System.