Maquila is the short form of the word maquiladora. It was originally associated with the process of milling. It has become the word for another kind of processing - the assembly of imported component parts for re-export. The maquilas in Mexico began as a border phenomenon in the 1970s. US firms set up assembly plants on the Mexican side of the border. They import components and raw materials duty-free, and reexport the finished product to the US.