Jacob Lawrence’s “The Migration Series, Panel No. 1: During World War I there was a great migration north by southern African Americans, between 1940 and 1941.” (Copyright Jacob and Gwendolyn Lawrence Foundation/Artists Rights Society)

Most of the time, Duncan Phillips, the founder of the Phillips Collection, is irrelevant to the average visitor. Although he created the museum, and put his stamp on its core holdings, one needn’t bother too much with his legacy. He died almost 50 years ago, and it’s the art that matters, not the collector. And rich people, after all, can buy art so promiscuously that it inevitably seems, in retrospect, that they were particularly ingenious on betting on all the right horses.

But a new exhibition, “Made in the USA,” makes a strong case for acknowledging Phillips’s brilliance and generosity as a collector. The show surveys the museum’s American holdings, and it gives one a much different and more vital understanding of the museum. This is not the usual, genteel Phillips Collection, a pleasant place to spend an afternoon with the French impressionists and their successors and imitators. Rather, it shows us a powerfully inter­connected genealogy of American artists wrestling with fundamental issues of representation, playing off of each other, building on collective accomplishment and pushing themselves into uncharted artistic territory.

It is, by the Phillips standards, a huge show, beginning in the ground-floor lobby, spilling out in a temporary exhibition gallery near the entrance to the courtyard garden, and occupying multiple rooms on the second and third floors. Over 200 works are on display, by more than 125 artists, from romantic 19th-century confections to the first stirrings of abstract expressionism in the middle of the 20th century.

The galleries are so stuffed that the whole thing feels a bit like a once-a-decade family reunion. Every bed is taken, the place is hopping, and everyone bears an uncanny resemblance to everyone else.

It isn’t necessarily a comprehensive survey of American art during this period, but in many ways it’s more exciting than an exhaustive overview. “Made in the USA” offers a strong, steady, consistent vision of one strain of American creativity, an ideal of American art that was always sober, serious, sincere and authentic, grounded in spiritual earnestness, with little trace of irony or cynical gamesmanship. Almost all of the works on display were acquired by Phillips, so there are strong family connections between them, making it easy to see relationships that might otherwise be obscure. And American art feels suddenly self-sufficient throughout the course of the period surveyed — 1850 to 1970 — rather than a long drama of European dominance that yields slowly and painfully to American maturity only after the Second World War.

Thomas Eakins, "Miss Amelia Van Buren," c. 1891, Oil on canvas, 45 x 32 in. The Phillips Collection, Washington, DC, Acquired 1927; on view at the "Made in the USA" exhibit at The Phillips Collection. (Courtesy The Phillips Collection/Courtesy The Phillips Collection)

One particularly evocative and representative moment in this exhibition is the new contextualization of the museum’s Rothko Room. Nothing about the room has changed, it is still a dimly lit little “chapel” for viewing four of Rothko’s canvases. But after spending a few hours with the work of John Sloan, John Marin, Arthur Dove and Georgia O’Keeffe, Rothko’s luminous, hovering, fuzzy-edged rectangles feel as connected to the past as they do to the contemporary abstract expressionists from the 1950s. These are not ruptures from tradition but further reflections on it, ongoing efforts to distill the essence of landscape and light to something elemental.

Even some of the artists who seem to have been peculiar fixations of Phillips are seen in a more sympathetic and revealing light. The cloud­like abstractions of Augustus Vincent Tack, who created a cycle of paintings for the Phillips music room, feel less decorative and more substantial in the context of the larger arc of American painting. One can imagine a young American artist in the 1940s and ’50s seeing these refined and meticulous confections of light and color and thinking: Imagine that same painting imbued with a little violence, a little more energy, a more sweeping, athletic sense of gesture. And voila, welcome to the world of Pollock and de Kooning.

For all the inter­connections, the basic spirit of the exhibition is variety and abundance. The homespun rusticity of Grandma Moses and the direct, narrative voice of Jacob Lawrence are only a room away from an exciting gallery of urban images, made by under-appreciated painters such as Ralston Crawford and Stefan Hirsch. A gaggle of impressionists leaves one with new appreciation for John Henry Twachtman, whose circa 1891 “Winter” can hold its own with anything from France at the time.

The exhibition opens with a room devoted to “Realism and Romanticism,” though already here you can see what becomes a recurring tendency in American art: a sense of painterly freedom unlocked by the natural world, rather than slavishly devoted to imitating it. The skies of Winslow Homer, the weird color nocturnes of Albert Pinkham Ryder, the mystical darkness of George Inness, all share a sense that nature gives the painter permission to experiment.

That permission was used exuberantly by younger generations that included Marsden Hartley, Marin, Rockwell Kent and Harold Weston. Kent’s “The Road Roller,” Hartley’s almost fauvist “Mountain Lake—Autumn,” Weston’s “Winds, Upper Ausable Lake” are all thrilling masterpieces, deeply connected to the natural world, not through ordinary means of representation but a more powerful process of intimation and suggestion.

Several artists connected to Alfred Stieglitz’s 291 Gallery (Marin, Hartley, Dove and O’Keeffe), the famed oasis of contemporary art in New York in the first decades of the 20th century, dominate much of the exhibition. A row of Stieglitz’s photographic “Equivalents,” monochromatic abstractions made by photographic cloud forms, struggle and ultimately succeed to assert their presence next to larger, color-saturated work. But the ethos of 291, the innocence of its early embrace of the European avant-garde and the American drive to mold those energies to new purpose, casts a long shadow over almost everything in the exhibition that post­dates the 19th century.

Amid all the variety, it’s encouraging to see how individuals stand out in the show. There is a bad habit, almost universal among those who visit museums, of mentally dividing the familiar from the unfamiliar, the brand-name artists from the lesser lights whose names one struggles to rescue from obscurity and forgetting. Partly that has to do with the art and the artists; mediocrity isn’t memorable. Partly it has to do with lazy habits of the mind.

But this exhibition allows artists who may be unfamiliar to rise above the general din. Phillips and the curators who succeeded him somehow managed to find striking paintings by many artists who never became household names. Charles Burchfield’s “December Moonrise,” from 1959, is a sit-down-and-gape stunner, a landscape that feels pressed against an icy, frost-covered window pane, exerting a goose-bumps chill through its sense of impotent light lost in a frozen sky. Paul Dougherty’s 1912 “Storm Voices” is just as memorable and evocative as the late seascapes and coastal paintings of Homer.

“Made in the USA” doesn’t define American art, nor does it offer any clear sense of whether there’s something essentially American that runs through the work on display. It does, however, leave one wishing there were more collectors like Phillips running around today. He had an eye, and he clearly had a strong commitment to artistic independence, especially independence from the fads of the moment or strict ideologies about what art must or must not do. Those two guiding principles encompassed a magnificent diversity of art, and that diversity in the end feels like his greatest accomplishment.

Made in the USA

is on view at the Phillips Collection through Aug. 31. For more information, visit www.phillipscollection.org.