Factory work seems so dangerous and grueling.
Absolutely. Factories typically have lots of buildings and complex machines that do constant work. All the people and machine residue can make quite a mess.
yea its very heavy duty and monotonous work
Speaking of, factories actually came about during the Industrial Revolution. An exciting time, but also a very dirty and unsanitary one as well as space requirements were a constant struggle
Yea and not only was it hard and dangerous but they had kids working them as well
Glorified sweatshops, yes. Modern factories have large warehouses and assembly lines, but back then it was all labo intensive 
Yea some of them required much more attention to detail.
Yup and, of course, transportation. Most large factories are usually near multiple nodes of transport such as rail, highway, or water docks