Thomas Hart Benton's lithograph "Departure of the Joads" from 1939 depicts the main characters from "The Grapes of Wrath." (National Gallery of Art, Washington)

In the last room of the National Gallery of Art’s “Three Centuries of American Prints” exhibition is a curious wall label for a 1989 poster by the Guerrilla Girls, a feminist art group that addresses sexism and racism in the art world. The poster is a classic Guerrilla Girls provocation, showing a nude woman from behind, lounging on a sofa, with an oversize gorilla head. It asks: “Do women have to be naked to get into the Met. Museum?”

Since the Guerrilla Girls started challenging prominent museums to better represent female artists more than 30 years ago, posters such as this have taken on iconic status. As the wall label explains, this particular one, in fine condition, was “a gift of the Gallery Girls in support of the Guerrilla Girls.”

And who are the Gallery Girls? “The Gallery Girls was formed in 2007 as an informal group of Gallery curators, conservators, exhibition designers, and other employees to support the purchase of artworks that meet the Gallery’s acquisition standards and that were created by artists who are under-represented in the Gallery’s collection,” says the National Gallery. The Gallery Girls aren’t officially related to the Guerrilla Girls, but share a fundamental mission: bringing inclusiveness, balance and diversity to the artists represented in the National Gallery.

The discovery of the Gallery Girls gift in the last room of this exhibition gives the whole show a pleasing symmetry. The first and last rooms of the show are full of bold, noisy, challenging work, prints that capture both the raucous nature of democracy and the inherently freewheeling nature of the medium itself.

That was, according to curator Judith Brodie, intentional. The early days of American printmaking are thus linked to the present moment, emphasizing fundamentally democratic currents in American prints that have had far-reaching impact on the arts and culture in general.

Robert Havell Jr., after John James Audubon. "American White Pelican," 1836 hand-colored etching and aquatint. (National Gallery of Art, Washington)

Unlike paintings and sculpture, prints are designed to circulate and reach wide audiences; they are to painting and sculpture what the Internet is to the book or printed newspaper. They are capable of being a fundamentally disruptive medium.

Throughout its run, “Three Centuries of American Prints” has attracted better than usual crowds, perhaps because the show, which closes on Sunday, has an appeal that goes beyond a standard art-history narrative. It traces the evolution of the form’s early forays by American craftsmen working in the English colonies in the 18th century through the rapid development of world-class skills in the later 19th century to the present, charting the ultimate breakdown of any clear definition of what prints are and how they function.

But the show is also full of the drama of American life and history. Among the most crudely made images in the show is one of the most historically riveting: Paul Revere’s 1770 engraving, “Bloody Massacre,” a hand-colored image based on an original by Henry Pelham, showing an incident in which British troops fired into a mob of Colonial protesters, killing five and wounding six others.

Revere, a silversmith and a political firebrand, used his engraving skills to produce a clumsy but effective broadside of the attack, with three columns of doggerel printed underneath: “Unhappy Boston! See thy Sons deplore,/Thy hallow’d Walks besmear’d with guiltless Gore.”

Originals of this print are very rare.

“It wasn’t the sort of thing you would save,” says Brodie, who along with co-curator Amy Johnston explains that it is not the sort of print that the National Gallery usually acquires. It is, by no means, a work of fine art. It’s inclusion in the gallery’s collection, and in this exhibition, is for its historical importance, and as a representative example of early printmaking by Americans in America (as opposed to several more professionally executed 18th-century works by Europeans who visited America or treated American themes).

Frances Flora Palmer. "A Midnight Race on the Mississippi," 1860 color lithograph with hand-coloring. (National Gallery of Art, Washington)

If nothing else, it also underscores the role of silversmiths in the evolution of printmaking. Engraving was an essential part of silver work, and making a print from an engraving was a logical extension of the silversmith’s skill set.

And so the exhibition curators take a liberal view of the American print canon, not limiting themselves to works that earn their inclusion based only on artistic merit. In the early 1860s, the Currier and Ives company, which billed itself as “the Grand Central Depot for Cheap and Popular Prints,” distributed colored lithographs by Frances Flora Palmer depicting steamships on the Mississippi, and the show includes two of them.

“Normally we don’t collect Currier and Ives,” says Brodie, and these mass-produced prints do look rather humble in the same room with the enormous and masterfully made prints of John James Audubon’s “The Birds of America” series. But they help tell the larger story of America in the years leading up to the Civil War, the story of Manifest Destiny, westward expansion, internal discovery of the continent, with the implied message that it was a space to be discovered, conquered, held and exploited.

By the second half of the 19th century, American artists were circulating in the larger, cosmopolitan art world, and the exhibition becomes more focused on the artistic aspects of the medium and masterpieces thereof. Many of the names are familiar: James McNeill Whistler, John Singer Sargent, Thomas Moran, Mary Cassatt. There’s a marked change in tone, and subject matter. Landscape recedes, urban life intrudes, and domesticity comes into view. In the early years of the 20th century, the brawling incident of the early rooms still recurs, from time to time, especially in works by John Sloan and George Bellows. But as the exhibit proceeds, the few remaining landscapes begin to feel empty, nostalgic and even a bit forlorn, as in Edward Hopper’s 1920 “American Landscape,” or Thomas Hart Benton’s “Departure of the Joads,” commissioned by Twentieth Century Fox to promote its film of John Steinbeck’s “The Grapes of Wrath.”

In many ways, printmaking falls apart in the last room, not into creative disarray, but into such formal variety that it would be hard to give any single, coherent definition of what a print is today (consider Claes Oldenburg’s “Profile Airflow,” a molded polyurethane three-dimensional “print” of a car, or Robert Rauschenberg’s “Cardbird II,” an assemblage of corrugated cardboard fragments). But even here, the old tendency to register the political currents of the moment survives in the broadside, big-tent, wide-audience appeal of works such as Jenny Holzer’s “Truisms,” a printed poster full of provocative social observations (“Sin is a means of social control” and “Stupid people shouldn’t breed”).

And so one is thankful for the Gallery Girls’ gift of the Guerrilla Girls’ classic criticism of the Met in New York. It makes perfect sense in this context, and it continues the best of the democratic tendencies of the medium. Its inclusion is the art equivalent of what language philosophers call a “performative utterance,” a statement that not only describes or says something, but makes something tangible happen in the real world.

The simple act of including the Guerrilla Girls poster in this context makes it art. And in becoming art it chisels away at the neglect of female artists that it decries. And so the show ends on a note as radical as it began, with a statement about power and fairness, made by a work that began life as a provocation, entered the art gallery through a side channel, and became canonical in the process.

Three Centuries of American Prints is on view at the National Gallery of Art through Sunday. For more information visit nga.gov.