Your fortress's total Created Wealth is visible on the status screen once you have a bookkeeper with at least novice appraiser skill (though your bookkeeper still needs to do quite a bit of work to achieve and maintain exact figures). All objects with any value (including mined-out areas, bridges, engravings and every kind of created good) will be included in the total. Artifacts are usually one of the largest influences of fortress wealth. Artifacts made of precious resources and heavily decorated can easily be worth thrice the value of the rest of your fortress in the early years.-
Items made off-site are not counted in your total fortress wealth. Their value is listed under "imports." This only applies until you change the item in some way. For example decorating specifically imported objects and goblin loot; those will be substracted from the import figure and added to their respective division of your created wealth.
While prepared meals can be quite valuable and it's to a much lesser extent possible to amass wealth from booze, unless forbidden, these items tend to get consumed by your gluttonous dwarves at an alarming rate, reducing your wealth. Among other factors, the value of a meal makes it more desirable, too. This loss is to be expected, and on the plus side quality food does provide a source of happy thoughts.
Wealth influences or triggers various game features, such as goblin sieges, the arrival of nobles and megabeasts, the number, and probably time of arrival, of immigrants, which can lead to loads of fun if a early and unprepared fortress increases their value drastically after creating a valuable artifact.
 Building fortress wealth
Good ways to building wealth include:
- Checking for promising stone layers when selecting your location.
- Searching for and using valuable metals (e.g. gold, aluminium, or platinum) early on
- Choosing proficient dwarves on embark; experienced dwarves work faster, and make higher quality goods.
- Using more valuable, but still abundant stone (e.g. obsidian or flux) for "everyday items"
- Smoothing and detailing walls
- Check item value for clues on what items are valuable and how processing boosts wealth
- Build a steel armor industry
- Encrusting/decorating objects with highly skilled craftdwarves
- Assisting dwarves in strange moods, especially leaving high value gems, giant cave spider silk, and adamantine/aluminum/platinum for decorations nearby