Salt pork isn't just American, of course; it has been used for hundreds of years by sailors and other travelers since it would stay tolerably fresh for long periods of time. It used to be made from any leftover bits of pork and pork fat left after butchering, which would be pressed into a barrel and salted down for preservation. It was a standard ration on ships, for soldiers and for sailors. Hardtack and salt pork were basic rations during the American Civil War.
Now, however, salt pork is made from pork bellies - just like bacon. It's much fattier than bacon though, and it's not smoked or cured like bacon. That fat and saltiness make it a good base flavoring ingredient for many dishes; it's traditionally used in Boston baked beans and other thrifty New England dishes.
Salt pork is a marvelously cheap and long-lasting meat. If you just want a little meaty flavoring for a pot of beans or dish of greens, it's a good option. Cheaper than bacon, and fattier, salt pork can be slowly rendered down to cook and flavor cheap vegetarian ingredients.
We use just a few small slices for our cooking. We recently made a pot of our Braised Green Beans. Green beans need to be cooked for a long time to let their flavor really emerge; if you haven't tried slow-cooked green beans you're missing something! That slow cooking is also benefited by a little meaty flavor. So we slowly cooked down a few small slices of salt pork, then sauteéd the onion and garlic in that fat - no extra fat required.
The sweet, mellow taste of the pork infused the whole dish - and we only used about a third of our $2.69 package of salt pork.
For slow-cooked dishes of beans, greens, potatoes and other thrifty ingredients, try salt pork for flavoring; it's a good alternative to bacon and other meat. Check out our post on beans and see if you can work a little salt pork into your next pot: How To Cook Beans