A century before the West dammed its rivers, New England's mill dams had already wiped the Atlantic salmon out of the Connecticut and the Merrimack. The lesson was on the books. The episode asks why it did not carry west and weighs three readings fairly, ignorance, indifference or greed, without a tidy verdict.
How to weigh ignorance, indifference and greed, and at what dates, is left open. A strong case holds that no channel existed for the Merrimack's lesson to reach Columbia engineers, so 'they should have known' may be hindsight.



