During the 19th century, the spread of factories throughout new england resulted in: a. improved water quality in the northeastern united states. b. a decline in the demand for new railroad construction c. fewer job opportunities for immigrant laborers. d. more american workers relocating to urban centers.

D. more American workers relocating to urban centers.
The factory system was first adopted in Britain at the beginning of the Industrial Revolution in the late 18th century and later spread around the world.[1] It replaced the putting-out system. The main characteristic of the factory system is the use of machinery, originally powered by water or steam and later by electricity. Other characteristics of the system mostly derive from the use of machinery or economies of scale, the centralization of factories, and standardization of interchangeable parts.