Interlake Steamship builds flexibility into first US laker in 40 years The Interlake Steamship Co. has been moving freight on the Great Lakes for generations. Its newest ship, Mark W. Barker, will build on that tradition for years to come.   The 639-by-78-foot Mark W. Barker is the first U.S.-flagged Great Lakes freighter built in almost 40 years, and it’s…