This building is designed to store a key resource of the game: the building materials needed for the construction and improvement of base buildings and further defensive structures. The game begins with a first level Material Depot. Upgrade it to increase the amount of building resources you can store, and the rate that they replenish.
In June 1939, Congress approved a special law establishing United States reserves of strategic raw materials. On June 25, 1940, another law was passed which allowed private corporations to gather strategic raw materials for military development and the production of various military equipment. These corporations also enjoyed government loans for the construction and purchase of factories, equipment and resources.