Seattle and New Orleans seem as different as two cities under the same flag could be. Big Easy and Lazy B. Caribbean and semi-Nordic. Old Man River and Salish Sea. Filé gumbo and clam chowder. Professor Longhair and Dr. Science. Hurricanes and earthquakes. Fearsome hills and even more fearsome flats. N’er the twain shall meet. Essential Arts, a new Seattle nonprofit, has a different idea. It’s brought together both cities’ artists—six writers,...