Winslow Homer’s career was a bifurcated one. In his early professional years, he was a New York–based illustrator for Harper’s and other publications, chronicling most notably the Civil War and its immediate aftermath, and working mostly in engravings while painting the occasional oil composition. The late-career Homer we know much better: he the solitary painter of Prouts Neck and master of the maritime sublime. Between these two periods, Homer traveled extensively and began to experiment in both medium and style, working for the first time in watercolor. He also gravitated towards the seashore, spending summers around the Northeast and in particular Gloucester, Massachusetts. “Homer at the Beach: A Marine Painter’s Journey,” now showing at the Cape Ann Museum in Gloucester, presents a chronological story of this metamorphosis.