People who live in Muskegon drive past the Mart Dock constantly and have, in my experience, only the vaguest idea what happens behind the fence. It is a fair question, so here is the answer.
Max McKee is president of The Mart Dock, and the honest summary of the operation is that it does three unrelated things on the same 40 acres: it moves bulk cargo, it services vessels, and it stores an enormous quantity of other people's property through the winter.
Cargo
Muskegon is a natural deep-water harbor, which on the Great Lakes is less common than it sounds. Muskegon Lake connects to Lake Michigan through a dredged channel deep enough for commercial lake freighters, and the Mart Dock sits on the protected side of it.
What moves across the dock is mostly aggregate — sand, stone, and similar bulk material that is cheap per ton and therefore only economical to move by water. A single vessel carries what would otherwise require several hundred truckloads on the highway, which is the entire argument for keeping a commercial port downtown.
Vessel Servicing
The second business is servicing ships. Great Lakes vessels need somewhere to lay up, take on supplies, and have work done, and a dock with depth alongside and road access can provide that. This is unglamorous, seasonal, and dependent on having the right water depth at the right berth.
It also means the dock keeps equipment and skills on hand that a pure cargo terminal would not — which is part of why the historic vessels here have stayed serviceable rather than deteriorating at anchor somewhere.
Storage
The third business is the largest indoor and outdoor storage facility for marine vessels and land vehicles in the region. Boats, cars, and RVs come in when the weather turns and go out in spring. In a state with real winters, this is steady, predictable work, and it uses acreage that would otherwise sit idle for five months.
Storage is also what makes the rest viable. Cargo volumes fluctuate with construction cycles and the shipping season is short; storage revenue arrives on a schedule and does not care what the aggregate market is doing.
Conclusion
None of this is exotic. It is a harbor with depth, a dock with acreage, and three businesses arranged so that the slow season for one is the busy season for another. The same berths also host passenger cruises from the same dock in summer. More on Max McKee's stewardship of the port.