Kevin O'Neill

Along most of America's coastline, crustaceans get boiled. Sometimes in plain old Yankee water. Sometimes in spicy Cajun stock. Whatever the liquid, there's a whole pot of it bubbling away. Whatever the seafood — Maine lobster, Carolina blue crab, Louisiana crawfish — it takes the plunge.

And that's just wrong.

Ask anyone in Maryland, where there's just one way to cook a crab. That way is steaming.

"I think we're pretty much the main steamers as far as I know," said John Shields, chef-owner of Gertrude's restaurant and author of several books on coastal cooking, including "The Chesapeake Bay Crab Cookbook." "Florida, the Carolinas,...