J.J McDonnell was founded in 1945 and was originally located in the downtown Baltimore Seafood Market. In the early days of the business, fresh fish product was purchased from the docks and then resold to buyers from a vendors stall in the market. Over the years J.J McDonnell became known for its oysters, crabmeat and shrimp. In 1984, the firm relocated its operations to the Maryland Seafood Market in Jessup, Maryland.