U.S. pioneer builder of covered timber truss bridges (covered bridge).

A millwright, he was also a self-taught carpenter and architect, and in 1792 he built the Essex-Merrimack Bridge over the Merrimack River near Newburyport. Composed of two trussed arches meeting at an island in the river, the bridge remained in use for more than a century and was the prototype of the numerous bridges he later built throughout New England.

Palmer's most noted work was the completely enclosed Permanent Bridge (c. 1806) over the Schuylkill River at Philadelphia. In use until destroyed by fire in 1875, the Permanent Bridge proved the value of, and set the style for, covered bridges in the United States.