Because they provided water power to run the machinery and a place to dump their waste
Factories need transportation to bring in supplies needed inside the factory and to ship what is produced in the factory out to stores, the public, etc. Early factories didn't have the use of railroad and trucking transportation, so the quickest way for these early factories to bring things to the factory and ship goods out of the factory was by water. Therefore, they were built along waterways like rivers.
Near water
Mainly in the eastern half of the US, cause the west wasn't explored yet. They were usually along rivers so that the water could be used as power. It was also more in the Northern half, like PA or NY.
it had to be next to rivers
The first U.S. factories were built in New England near rivers and streams to harness water power for manufacturing. Cities like Lowell, Massachusetts and Pawtucket, Rhode Island were early industrial centers in the United States during the 19th century.
New England
At the beginning of the Industrial Revolution, factories were commonly built next to flowing rivers or other water source because people used the water as an energy source to run the machines in the factory.
So they could have a water source.
Fall Line!! = )
So they could have easy acces to fishing, and a water source to clean there clothes ;-]I hope this helped :D
beaause they can get the water from the lakes