The cargo vessels that work the Great Lakes are known as Lake freighters or Lakers. The most well-known is the SS Edmund Fitzgerald, the last major vessel to be wrecked on the Lakes. These vessels are traditionally called boats, not ships.

Lakers are generally bulk carriers, that is they carry loads of rocks, salt or grain in large holds - not in containers. The earlier ships required unloading machinery at the docks but modern Lakers are self unloaders which allows them to unload faster and in more ports.

The most common cargos on the Great Lakes are taconite, which is a type of iron ore; limestone, grain, salt, coal, cement and potash. Much of the cargo goes to support the steel mills for the auto industry which was centered around the Great Lakes because of the ease of Lake transport.

The largest vessels on the lake are the 1000 footers (300 m). These vessels are between 1000 and 1013 feet (305 and 309 m) long, 105 feet (32 m) wide and of 56 feet (17 m) in draft. They can carry as much 78,850 long tons of bulk cargo although their loading is dependent on lake water levels especially in the channels and ports. A dozen of these giant ships were built, all constructed between 1976 and 1981, and none has ever sunk. The most powerful of these, the Edwin H. Gott , carries two diesel engines driving twin propellers and is rated at 19,500 brake horsepower. This generates a top speed of almost 17 mph (27 km/h).

More common are boats in the 600 and 700 foot (183 and 213 m) classes and these continue to be built. These vessels vary greatly in configuration and cargo capacity, being capable of hauling between 10,000 and 40,000 tons per trip depending on the individual boat.

Since these vessels all have to proceed through the locks of the Great Lakes Waterway they have features in common, and their appearance differs from similar sized ocean-going freighters. They are narrower and generally longer. The largest deep lock at the Soo is the Poe Lock which is 1,200 feet (370 m) long and 110 feet (34 m) wide. Thirty vessels on the lakes can only pass between Lake Superior and Lake Huron via this lock although none approaches the lock's size. Many Lakers are restricted to the Lakes, being unable to navigate the St Lawrence Seaway whose locks allow a maximum vessel size of 740 feet (226 m) in length or 78 feet (24 m) in breadth.

Where the superstructure of an ordinary freighters used to have the bridge in the center of the vessel, lake freighters typically have the bridge and associated superstructure right up in the bow. Traditionally they had a second island, over the engine room, right aft in the stern. These dual cabined boats were constructed between 1869 and 1974. The R.J. Hackett premiered the style and the second Algosoo was the final vessel designed this way. More recently built lakers, like the Seawaymax CSL Niagara, have a single large superstructure island right astern.

Since the freshwater lakes are less damaging then the salt water of the oceans, many of the Lakers remain in service for long periods and the fleet has a much higher average age than the ocean-going fleet. Boats of older than 50 years are not unusual. The E.M. Ford had the longest career, having been built in 1898 and still sailing as perhaps the last steamer on the lakes ninety-eight years later in 1996. In 2001 it was still afloat as a stationary transfer vessel at a riverside cement factory. The J.B. Ford built in 1904 last sailed in 1985 and in 2001 served in the same capacity as the E.M. at a different cement works. Several decorated World War II veteran boats still are in active, although civilian, use on the Lakes.