Put all the following ingredients in a large pot. Add enough water to just cover all. Bring to a boil, reduce heat and simmer until the peas are tender, about 2 hours. Skim off any foam that rises to the surface.
2 or 3 carrots, scrubbed and sliced
2-3 stalks of celery, sliced
1 large onion, coarsely chopped
pepper, a few grinds
1 pound split peas
Once the peas are soft add salt to taste.
To make this a vegetarian split pea soup, leave out the ham (obviously), add an additional carrot and onion and use vegetable broth instead of water.