Raw material - they should locate closer to the raw material if it is large and heavy so it costs less to transport the material
Market - factories just near the target market can have lower transport costs when transporting their product
Transport facilities - a rail network or an airport is beneficial for a factory to import raw material and export products
Workforce - some factories locate near colleges/schools for an educated workforce
Personal preferences - some locate a factory in their hometown
Industrial inertia - when an industry does not relocate to an area when it makes sense to do so, possibly because of the connected history the factory has had in the area.