THERE HAVE BEEN long-standing troubles with the ways in which we categorize artists. Folk, outsider, visionary, self-taught, naive, grassroots: These words, by turns deployed, debated, rejected, and qualified, are weighed down by so much more than they delimit. Since the advent of modernism, such labels have been attached to various American artists who did not emerge via fine-art institutional pedigrees, and to diverse forms of artmaking that have been deemed peripheral to the prevailing aesthetics trafficked by the decidedly metropolitan, market-dominated centers of the self-proclaimed “art world.” Past exhibitions that have placed such work alongside modern, avant-garde, or “advanced” art—one winces at this last term, common in artspeak, because it suggests that its opposite is “regressed” or “backward”—have smacked of condescension based on class, race, ability, and region, and have made an ugly spectacle of difference to accentuate existing power hierarchies: Look what the poor house cleaners/nonwhite makers/disabled people/rural yokels managed to do!

“Outliers and American Vanguard Art,” skillfully curated by Lynne Cooke at the National Gallery of Art in Washington, DC, avoids the traps of drawing easy, false parallels and parading decontextualized “formal affinities.” Instead, the show contends that the outputs of the schooled and the unschooled have frequently converged; while she acknowledges that such distinctions cleave along lines of privilege, Cooke proposes the moniker outlier in lieu of that long list of previous designations. Outlier, defined as “beyond the statistical norm,” was selected by Cooke because it is “not freighted with negative associations,” but whether this new coinage will maintain her optimistic recasting is not yet clear.

With this ambitious undertaking, Cooke brackets three occasions in the history of American art when mainstream artists (and, to some degree, major museums) embraced and openly advocated for more marginalized painters, sculptors, builders, drawers, and quilters, creating fertile intersections that fueled formal innovation. These three moments: the “interwar period,” which spans 1924 to 1943, decades that included the Great Depression and World War II; the “long 1970s,” which Cooke understands as unfolding between 1968 and 1992, in the aftermath of the civil rights and women’s movements, counter-cultural revolutions, and gay liberation; and the years 1998 to 2013, which saw a revival of interest, not least among feminist artists, in amateur photography and the “women’s work” of textile craft practices. One gallery is dedicated to ancillary materials, featuring a slide show of experimental architectural environments, including James Hampton’s secret garage installation, Throne of the Third Heaven of the Nations’ Millennium General Assembly, ca. 1950–64, and Simon Rodia’s Watts Towers; recordings of music by Howard Finster and Sister Gertrude Morgan; and a vitrine displaying landmark publications that focused on the importance of tracing continuities between seemingly divergent traditions of making, such as the catalogue for the 1974 “Naives and Visionaries” exhibition at the Walker Art Center in Minneapolis and Robert Farris Thompson’s 1983 book Flash of the Spirit: African and Afro-American Art and Philosophy.

These periodizations are for the most part convincing, but the show’s opening rooms are its strongest: Here Cooke demonstrates the invigoratingly porous flows between academically trained and uncredentialed artists through carefully selected pieces predominantly from the early decades of the twentieth century. Deftly executed watercolors from the Index of American Design—a New Deal initiative that paid artists to chronicle vernacular functional objects and decorative art such as Shaker rugs and tables, whirligigs, and carousel horses—illustrate a literal intersection between the anonymous homespun maker and the named professional. Paintings by well-known figures from the first acknowledged waves of America’s avant-garde, such as Yasuo Kuniyoshi, Malvin Gray Johnson, Florine Stettheimer, and Charles Sheeler, are installed in proximity to carved-wood sculptures by lesser-known Latino artists José Dolores López and Patrociño Barela, expanding the received narratives about the country’s flourishing multiracial art scene in the ’20s and ’30s. Indeed, the entire exhibition attends to the ways that race and class have determined who is considered “inside” and who is defined as “outside.” The inclusion of multiple works by painters Horace Pippin, Bill Traylor, and Jacob Lawrence—along with pieces by limestone carver William Edmondson, who in 1937 was granted the first solo show by an African American artist at the Museum of Modern Art in New York—emphasizes the centrality of black aesthetics to American art across the inside/outside schema.

In the initial galleries, some of the exhibition’s subtler recurring themes are made evident, including the reverie of the dreamscape, the comforts of the material world, and the potency of the spiritual realm. Interestingly, there are at least two formal trajectories on offer, and they do not adhere to a norm-versus-outlier binary. Some artists seek to purge excess as they simplify their work, pushing toward schematization and abstraction; others follow a more baroque countervailing impulse, diving into intricacy, relishing accretion and ornament. Another thread woven through “Outliers” might be termed “interracialization”—solidarity across racial lines forged via pictorial homage—a gesture that can be seen in three portraits by black artists from the ’40s of white abolitionist John Brown, one carved by Henry Bannarn, one painted by William H. Johnson, and another painted by Pippin.

Though it functions as a hinge between the early and the later twentieth century, the section on the ’70s feels a little too baggy and protracted to hang together as a discrete era, and is comparatively underdeveloped considering the explosion of hobbyist, do-it-yourself, and psychedelic creations that energized everything from mainstream household décor to fashion design. Here one encounters Martín Ramírez, who spent many years of his life confined to a mental hospital, and whose work was collected and promoted—the show eschews the colonial-sounding “discovered”—by Chicago Imagist Jim Nutt. Ramírez’s inclusion is a reminder that many “outlier” artists were bound by economic, systemic, and physical circumstances that prevented their art from circulating as freely as it does now. A room devoted to Imagism segues into one that delves deeply into ’80s Southern black art, which includes some of the most compelling works in the show, such as vibrant mixed-media pieces by Steve Ashby. A section dedicated to West Coast “funk and junk” pairs mostly white Northern California assemblage artists like Bruce Conner, Roy De Forest, and William T. Wiley with post–Watts Rebellion African American artists Betye Saar, Senga Nengudi, Noah Purifoy, and John Outterbridge, illuminating the range of approaches to figuration as well as the varying uses of scavenged goods in these different regions. Given the exemplary ways that “Outliers” pays attention to the specificities of location with regard to production, it could have been more precise about the artists’ places of origin, perhaps by naming their home states or towns on the tombstone labels as is done in the biographical essays in the catalogue. As it is, almost everyone is identified as generically “American,” whereas particular attributions would have been more in keeping with the purview of the show.

Two minimonographic exhibits—one dedicated to the soot-and-saliva works of James Castle, the other to Robert Gober’s presentation of the paintings of self-surgery pioneer Forrest Bess—demonstrate the complex crossovers between the identifications “outsider” and “insider.” Castle’s drawing of his own works hanging in Idaho’s Boise Gallery of Art (now the Boise Art Museum) is a tour de force of meta-depiction; pages from Bess’s “thesis,” sent to art historian Meyer Schapiro, document a correspondence between two unlikely friends. Other artists’ stories—such as that of Ukrainian American Janet Sobel, a drip painter who used her son’s art supplies and became a sensation with émigré Surrealists—illustrate how quickly some go from toiling at home to being celebrated in the rarefied halls of modern art to falling back into obscurity.

As “Outliers” argues, this constant churning—this trespassing of the borders of high and low, this teetering between the unknown and the famous—is essential to the dynamism of American art itself. The risky installation of mural-size drawings by Henry Darger, a janitor with no formal education, near the work of Matt Mullican, who graduated from CalArts and sometimes hypnotizes himself to tap into the freedoms of the auto-didact, provocatively suggests that “outlier” is not only a financial or structural condition but may also be a state of mind. An especially well-formulated discourse on the transmissions between fine-art and vernacular photography includes work by captivating compatriots Lorna Simpson, Eugene Von Bruenchenhein, and Lee Godie. Zoe Leonard and Cheryl Dunye’s Fae Richards Photo Archive, 1993–96, is a collaborative photographic album chronicling the life of a fictional queer black actress; with its tender intermingling of the everyday and the extraordinary, it is one of the exhibition’s highlights. The exhibition of quilts by Gee’s Bend, Alabama, residents Annie Mae Young and Mary Lee Bendolph in proximity to textile-based abstractions by Howardena Pindell and Al Loving and a quilt-like oil painting by Mary Heilmann further blurs the boundaries between genres. Together these works offer a rich visual essay on how tactility has functioned as a resource for recent black and female artistic practices alike.

“Outliers” is implicitly feminist, featuring many women as well as artists, like Greer Lankton, whose gender, like their art, falls “outside” binary logics. (An excellent catalogue essay by Douglas Crimp elaborates on this topic; Darby English, Suzanne Hudson, Thomas J. Lax, Richard Meyer, Jenni Sorkin, and Jennifer Jane Marshall also contributed thoughtful texts.) With its suggestive alliance of women who make strategic use of elements both quotidian and exceptional—including Jessica Stockholder, Judith Scott, and Rosie Lee Tompkins—the last room of the exhibition, which is also its first, brings the viewer full circle, reasserting Cooke’s core interests in race, class, gender, and materiality. Have the barriers between these variously trained artists and their disparate practices truly dissolved? And would that dissolution erase the realities of how this work is unevenly valued, and how differently these artists are recognized and compensated? These are the difficult questions left unanswered by the exhibition, but “Outliers” makes the case that all of these artists—no matter where or how they learned their craft—have far outpaced our language for them.

“Outliers and American Vanguard Art” is on view through May 16.

Julia Bryan-Wilson is a professor of modern and contemporary art at the University of California, Berkeley, where she also serves as director of the arts research center.