The Boston Marathon route runs 26 miles from Hopkinton to the Boston finish line; the meandering Charles River winds 80 miles between those same points, flowing through 23 communities before emptying into Boston Harbor. This bird’s-eye view, produced in the early 20th century, looks southwest from an imaginary vantage point above the industrial city of Waltham. The river snakes through the western suburbs, passing such landmarks as the Waltham Watch Factory, the industrial complex at Newton Lower Falls, and the now-defunct Norumbega Park. Rail lines crisscross the landscape, evidence of the growth of these river-adjacent towns.