Kevin Gardner, an expert on stone walls, will offer a presentation on the New England landmarks on April 2 at 7 p.m. in the public library. The event is a joint program of the Tewksbury Historical Society and the library. The talk will explain how and why New England towns came to acquire their thousands of stone walls, their significance to the New England landscape, and how stone walls and other dry stone structures were built. Stone wall construction in Tewksbury dates to the town’s Colonial days, and many of the walls remain. The presentation is free and open to all, but those planning to attend are asked to reserve a seat by calling Robert Hayes at the library, at 978-640-4490, ext. 205, or by e-mail at rhayes@MVLC.org.