Shipment is one of the most popular maps in the Call of Duty series. One of the developers revealed in an interview that the map only made it into the game through a lucky accident.
Shipment is a very small map and has a very simple layout, which should make it more suitable for split-screen games on a single TV. The developers used the map as an internal test map during the development of the first Modern Warfare installment in 2007. And it was only through a mishap that Shipment finally ended up in the published version.