Chowder is any of a variety of soups, most of them thick and made with potatoes. To some Americans, it means clam chowder, made with cream or milk as New England Clam Chowder, or with tomato as Manhattan Clam Chowder. Corn Chowder is a thick soup filled with whole corn (maize) kernels. Chowder is often commonly associated with the New England region of the United States.
The recipe below for "New England chowder" is, oddly, not a clam chowder.
From the 1881 Household Cyclopedia
New England Chowder
Have a good haddock, cod, or any other solid fish; cut it in pieces three inches square, put a pound of fat salt pork in strips into the pot, set it on hot coals and fry out the oil; take out the pork and put in a layer of fish, over that a layer of onions in slices, then a layer of fish with slips of fat salt pork, then another layer of onions, and so on alternately until your fish is consumed; mix some flour with as much water as will fill the pot; season with black pepper and salt to your taste, and boil it for half an hour. Have ready some crackers (Philadelphia pilot bread if you can get it) soaked in water till they are a little softened; throw them into your chowder five minutes before you take it up. Serve in a tureen.
This is similar to the traditional Scottish soup cullen skink.
Daniel Webster's Chowder
Four tablespoonfuls of onions, fried with pork; a quart of boiled potatoes well mashed; 1 1/2 pounds of sea biscuit broken; 1 teaspoonful of thyme mixed with one of summer savory: 1/2 bottle of mushroom catsup; one bottle of port or claret; 1/4 of a nutmeg, grated; a few cloves, mace, and allspice; 6 pounds fish (sea-bass or cod), cut into slices; 25 oysters, a little black pepper, and a few slices of lemon. The whole put in a pot and covered with an inch of water, boiled for an hour and gently stirred.