Where were factories built in the northwest throughout the 1800s

At waterfalls along rivers

Factories were built near rivers and streams that provide source power to the northwest throughout the 1800s.

Explanation:

Most factories were located in these regions because people were willing to offer the places because of the poor soil and people were willing to resort to factory work for more comfortable transportation of finished goods.

Introduction of factories led to new centralized production methods that confirmed the mills and made production rely on merchandize. This is because of the availability of steam and water power that was important in driving the machines.