Factories arose with the introduction of machinery during the Industrial Revolution so they have been around for many years
In what years was the industrial revolution?
Somewere around the 1970s, Early factories that contained small amounts of machinery
1970s?  That doesn't seem right?  I thought it was back in the 1800s?  
It was 1760 sorry, And back then large factories tend to be located with access to multiple modes of transportation so many facilities under one roof.
Interesting.  Didn't they make a lot of pollution and smog?
Yeah back then laws were a lot more lax. Factories mostly make one kind of product and make it continuously. 
What was labor like in those factories back then?
, chemical reactors, pumps and piping – outdoors and operated from control rooms. Oil refineries have most of their equipment outdoors.
Discrete products may be final consumer goods, or parts and sub-assemblies which are made into final products elsewhere. Factories may be supplied parts from elsewhere or make them from raw materials. Continuous production industries typically use heat or electricity to transform streams of raw materials into finished products.
The term "mill" originally referred to the milling of grain, which usually used natural resources such as
Factory
A factory, manufacturing plant or a production plant is an industrial site, usually consisting of buildings and machinery, or more commonly a complex having several buildings, where workers manufacture goods or operate machines processing one product into another.
Factories arose with the introduction of machinery during the Industrial Revolution when the capital and space requirements became too great for cottage industry or workshops. Early factories that contained small amounts of machinery, such as one or two spinning mules, and fewer than a dozen workers have been called "glorified