Sort and wash peas; place in a large Dutch oven. Cover with water 2 inches above peas (about 5 to 6 cups); let soak overnight. Drain peas; cover with remaining water.
Wash ham hock. Add ham hock and onion to peas, stirring gently. Simmer, allowing some steam to escape, 1 hour or until peas are tender. Remove onion; discard. Remove ham hock; remove meat from bone. Dice meat; stir into peas. Add salt to taste.