In 2019, the library completed a $33 million renovation project, adding an additional 30,500 square feet (2,830 m2) to complement the historic Richardson Building.

The inscription in the entrance porch reads: "This building was erected in memory of Jonathan Bowers Winn from funds bequeathed by his son, for the use, benefit and improvement of the people of Woburn."

In it he established a characteristic basilical plan for such buildings: an off-axis entrance marked by a staircase tower; a vestibule opening into a high-ceilinged reception area; reading room(s) adjacent to the stacks; and an optional art gallery.

The building's polychromatic exterior is constructed of brownstone trimmed with lighter stone, sometimes laid in bands, and set in alternating colors over the main arches and the entrance porch.

Beyond the reading rooms are the two-story stacks that feature a tall 6-arch arcade on each side, topped by a wooden barrel-vaulted ceiling.

A statue of native son and notable scientist Sir Benjamin Thompson, Count Rumford, stands on the main lawn before the library.