© Denzil Green
Cornmeal is a very coarse meal made from certain types of sweet corn.
To make cornmeal, corn kernels are removed from the cobs, dried, then ground coarsely. The corn used is usually Dent Corn. The Cornmeal may be white, yellow or blue, depending on the cultivar of Dent Corn used.
The meal can be ground to different degrees of coarseness. Very coarse is used for polenta. Fine is used in quickbreads such as Johnnycake and muffins.
Steel-ground Cornmeal removes the husk and germ, so that it keeps far longer without going rancid. Stone-ground Cornmeal retains the husk and germ, but should be used up right away or stored in the refrigerator.
This is not the same thing as Corn Flour, Cornstarch, or Masa Harina.
You can make your Johnnycake (or cornbread) less granular by first boiling the Cornmeal with some of the liquid from the recipe. In fact, many recipes will advise you to do that.
One pound / 450 g uncooked cornmeal = 2 2/3 cups
1 cup uncooked cornmeal = 6 oz / 175 g uncooked = 4 cups cooked
You can keep corn meal for up to 1 year. Steel-ground can be stored at room temperature, though it will last longer in the fridge; stone-ground must be refrigerated or kept in the coolest place you have. Storage life of steel-ground at room temperature can be impacted by warmer kitchens, higher summer temperatures, etc.
When cornmeal has gone off, it will have a rancid smell — and taste to boot. You can prolong the lifespan of either type of cornmeal by up to several years by simply storing it in the freezer in a tightly-sealed container.
Literature & Lore
 Do You Know Cornmeal? United States Food Administration. Food Leaflet #2 of 7. 1917. Women’s Archives Minnie Fisher Cunningham Papers, 1914-1944 02/2006-010.