In the United States in the mid-1800s, what made factories different from small workshops?

Of course, the most obvious difference between these two
types of workplaces was their scale.  Factories were much bigger than small workshops. 
However, this is probably not the most important difference.  The most important
difference, I would argue, was in the different ways in which workers experienced each
work place.

In a small workshop, the worker was more like a
family member than an employee.  The owner of the shop and the workers tended to work
side by side on the same jobs.  The owner might be grooming one or more workers to take
over the shop or to set out on their own.  This was a relatively egalitarian system in
which people were treated as people.

In a factory, by
contrast, there was very little in the way of human relationships.  The workers were
simply workers.  They were similar to the parts of the machines they worked with. 
Because of this, they would have experienced their work as a much more negative and
impersonal thing than they would have when they worked in small
workshops.

Overall, then, the biggest difference is that
factories were impersonal places where a worker was just a worker, not a human being who
was important for their own sake.