- Note: This page has been written specifically for Civilization IV. However, there's a some material that would generalize to the other games as well.
A resource is a special commodity that gives bonus production to its tile, and also gives bonuses to all cities which have access to it. A resource on the map is called a tile resource if the context is unclear. A resource that a civ has access to is just called a "resource"; it would be nice if there were a widely-used term to disambiguate this usage from "tile resource", but there isn't. For the purposes of the wiki, we refer to tradeable resources as trade resources.
Seeing resources
Tile resources are shown on the main map using their own graphics. You can also turn on resource bubbles to more clearly locate them. Some tile resources will not be shown on the map until particular technologies are known; for example, horses are not shown until a civilization knows the Animal Husbandry tech.
The trade resources that each particular city has access to are shown on the upper right portion of the city screen in iconic form, along with the effect that the resource has in that city. Strategic resources have no direct effect; some of them allow the building of particular military units, while others offer a production bonus to the construction of some buildings or wonders. Luxury and food resources will give one or two points of happiness or health.
Accessing resources
There are several means to gain access to a trade resource. These are reviewed in this section.
Via tile development
The fundamental way one gets most trade resources is to "unlock" a tile resource by building its particular tile improvement on it. (Alternatively, forts also unlock all resources, however since they give no production bonus to the tile you should usually build the proper tile improvement.) The tile improvement which unlocks each particular resource is listed in its article. For example, gems are unlocked by a mine. To gain access to the trade resource in a city, all of the following conditions must hold:
- the civilization controlling the tile must have the technology to use that resource.
- the tile must have the right tile improvement (or a fort) to unlock the resource
- the tile must have trade access to the city.
Generally, to get trade access a tile will be road- or river-connected to a nearby city, which in turn is connected via land or sea to the city in question. When you build a road to a resource tile which you've improved, this is called hooking up that resource.
Via technology
There are three high-tech trade resources, hit movies (
), hit singles (
), and hit musicals (
), which are created via winning the tech race to particular technologies. When a civilization has won such a race, it obtains a certain number of the associated hits into its trade network. (The particular number of resources varies with the map size -- more resources for larger maps.) Hits cause happiness in any civ and may be traded just as any other trade resource.
Via trade
Trade resources can also be gained by trading between civilizations. With trade access, one civ can make a deal with another to supply a trade resource, in return getting money or some other trade resource.
Via a corporation
There are two trade resources, oil and aluminum, which can be accessed in a city by having a corporate branch there. Oil is available in all cities with Standard Ethanol. Aluminum is available in all cities with Aluminum Co.
Lists of resources by type
There are three main subtypes of resources: strategic resources, luxury resources, and food resources. These are described below, with a listing of the resources of each type.
Strategic resources
All strategic resources give +1
on their tile regardless of what tile improvement it may have. Most of them give additional hammers when unlocked by the proper tile improvement.
Most strategic resources allow the building of certain military units, for example, a city must have access to horses to build mounted units, iron for swordsmen, or uranium for the nuclear missile. Most of them also give a +100% production bonus to certain buildings. Marble and Stone are exceptional in that they do not permit any military unit, and one or the other of them gives +100 to the building of most wonders.
Luxury resources
All luxury resources give +1
on their tile regardless of what tile improvement it may have. Most of them give additional commerce when unlocked by the proper tile improvement.
All luxury resources give +1 
to cities that have access to them. Many give an additional +1 with an appropriate building, whereas others give +1
. The "Hit XXX" resources are exceptional in that they have no tile resource; access to them is obtained only by being the first to complete particular techs.
: Dye- : Fur
- : Gems
- : Gold
- : Hit Movies
- : Hit Musicals
- : Hit Singles
- : Incense
- : Ivory
- : Silk
- : Silver
- : Spices
- : Sugar
- : Whale
- : Wine
Food resources
All food resources give +1
on their tile regardless of what tile improvement it may have. All of them give additional food when unlocked by the proper tile improvement.
All food resources give +1 to cities that have access to them, and an additional +1 with an appropriate building.
