A knee-high pipe sticking out of the ground not far from a school. A gurgle in a pond on rolling farmland. A patch of forest undergrowth hiding a long-forgotten, leaking oil well. Relics like these ...

A Times-Picayune analysis found that more than 3,600 oil wells drilled on land or in marsh are now in open water. To do so, the newspaper used the U.S. Geological Survey’s historical shoreline maps.

The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their ...