Two hundred years ago this summer, Maj. George Armistead commissioned a flag maker by the name of Mary Young Pickersgill in Baltimore, Md., to sew two flags for Fort McHenry at Baltimore Harbor. One of them would be 30 feet by 42 feet, large enough the British could see it from a long distance across the water as it loomed over the star-shaped fort. Susan Campbell Bartoletti details the scope of this work through the eyes of Mary’s daughter, Caroline, in her book, “The Flag Maker.”