Henri Rousseau’s “To Celebrate the Baby,” 1903, a monumental portrait of a healthy youngster, leaves one wondering what is going in this enigmatic composition. Courtesy of Kunstmuseum, Winterthur.

The exhibition is organized by themes, starting with Rousseau’s allegories and paintings on patriotic themes. His fervent nationalism was reflected in the spectacularly colorful “A Centennial of Independence” of 1892. It shows gaily garbed figures celebrating the Republics of 1792 and 1892 by dancing between rows of flags and in front of a tree festooned with pennants representing liberty and equality.

The affinity the army veteran felt for the military imbues “The Artillerymen,” circa 1893-95, with palpable charm as 14 haphazardly arrayed soldiers pose around their cannon.

Perhaps because he had been a soldier, Rousseau hated war. His attitude is reflected in the eye-popping, surreal “War” of 1894. In his apocalyptic vision, a wild-eyed, sword- and torch-bearing woman in white (“Discord on Horseback”) and a galloping black horse fly over a barren landscape littered with bodies of the dead and dying. Bloody arm stumps and ravens feasting on bloody remains of victims add to the horror of the carpet of corpses. “War” ranks with Francisco Goya’s “The Disasters of War” and Picasso’s “Guernica” among powerful indictments of the horrific consequences of war.

In 1907, shortly before a conference at The Hague on the settlement of international disputes, instigated by President Theodore Roosevelt, Rousseau painted a fascinating, idealized image, “The Representatives of Foreign Powers Coming to Greet the Republic as a Sign of Peace.”

Depicting an imaginary meeting in Paris, it shows Marianne towering on the left, symbolizing the French Republic, extending the olive branch of peace to foreign dignitaries gathered under a dark red canopy topped by international flags. A show-stopper when exhibited at the Salon des Indépendants, “The Representatives” was bought by Picasso – one of several Rousseaus he displayed in his Paris studio.

While laboring on large-scale canvases for salons, Rousseau turned out modest paintings offering peaceful views of suburban landscapes that would appeal to middle-class Parisian buyers seeking familiar scenes to decorate their homes. Whether depicting houses or a sawmill surrounded by trees and foliage, these images are free of the increasing chaos of the modern metropolis that Paris had become.

In his first jungle painting, “Tiger in a Tropical Storm (Surprised!),” 1891, Rousseau concocted a dramatic composition based on visits to the botanical gardens, zoo and Museum of Natural History in Paris and images of distant lands from books and magazines. Courtesy of The National Gallery, London.

“The Customs Post,” circa 1890, showed one of the many checkpoints that at the start of the Twentieth Century still encircled the outskirts of Paris along the old city fortifications. The accuracy of the details underscore Rousseau’s familiarity, as a customs employee, with the scene.

Signs of technological progress, in the form of telegraph poles and a gas lamp, punctuate the image of pedestrians walking under glowering skies in a village south of Paris in “View of Malakoff, Paris Region,” 1908.

Rousseau came to know the city well, as documented in “View from the Quai Henry IV,” 1909, which may contain a self-portrait in the foreground.

Some of the most unusual, occasionally unsettling, Rousseau works were portraits of his wives, neighbors or friends, which he sold quite reasonably. His fondness for children led to portrayals of dignity and intensity, as in “Boy on the Rocks,” 1895-97, and of fierce independence in the chubby, monumental figure dangling a harlequin puppet in “To Celebrate the Baby” of 1903.

The props featured in the intriguing “Portrait of Monsieur X (Pierre Loti),” circa 1910, reflect the predilection of the sitter, a naval officer and travel writer, for dressing up in Middle Eastern costume and for loving cats.

Picasso’s collection of Rousseaus began with his purchase in 1908, for a tiny sum at a second-hand shop, of “Portrait of a Woman,” 1895. Picasso never parted with this depiction of a monumental, dignified, black-gowned young woman standing on a balcony in front of an open window. It reminds one of Frida Kahlo’s head-on self-portraits.

Having been introduced to Rousseau by artist Max Weber, Picasso celebrated his acquisition of “Portrait of a Woman” with a famous banquet in Rousseau’s honor in his studio. The older painter, seated on an improvised throne, was toasted by guests who included Apollinaire, Braque and Gertrude and Leo Stein.

Garbed in a black velvet suit, striped stockings and black boots, Henri Rousseau’s “Boy on the Rocks,” 1895-97, maintains his dignity as he sits in an “Alpine” landscape. Courtesy of National Gallery of Art, Washington.

“Portrait of a Lady,” 1895-97, is a flattened, full-length likeness of Rousseau’s handsome, pink-cheeked first wife, Clemence, who died in 1888 after 20 years of marriage. Posed in black in a garden setting, she is accompanied by a kitten playing among the pansies.

“Painter and Model,” 1905-06, showing Rousseau painting a portrait of his second wife, Josephine, in an Edenic setting, is filled with naïve charm. It was bought by avant-garde pioneer Kandinsky, who praised the artist as “the father of a new realism.”

Rousseau presented himself and his second wife as an upright, sober, aging bourgeois couple in “Portrait of the Artist with a Lamp” and “Portrait of the Artist’s Second Wife,” both 1900-03. A man of his times, he depicted himself as the stronger of the two, whereas Josephine appears aged and vulnerable. Indeed, she died shortly after completion of the double portraits. Picasso, who purchased both likenesses in 1938, hung them in his bedroom.

In a less serious vein, “The Football Players,” 1908, is an unorthodox group portrait in which four merry athletes cavort in a clearing in the woods. It freezes the action in Le Douanier’s distinctive style.

Like his later jungle pictures, Rousseau’s numerous forest paintings are filled with both enchantment and mystery. In “Promenade in the Forest,” circa 1886, a fashionably dressed woman holding an umbrella seems out of place as she pauses on a path under spindly trees. Moonlight throws an ethereal glow over the brightly costumed couple silhouetted before leafless trees in “Carnival Evening,” 1886, one of Rousseau’s most ambitious and accomplished early paintings.

Rousseau’s loyalty to the salon, where he exhibited for years and made his name, animated “Liberty Inviting Artists to Take Part in the 22nd Exhibition of the Societe des Artistes Indépendants,” circa 1905-06. Here, beneath an angel-like figure personifying liberty and fame, artists and carts bearing paintings head for the site of the annual show. The elegant lion in the center, peacefully protecting the inviolability of artistic freedom, surmounts an honor roll of artists associated with the salon, including Pissarro, Seurat, Signac and Rousseau.

Rousseau’s most famous paintings of jungle scenes drew on popular fascination with faraway places and cultures, engendered by the expansion of France’s colonial empire in the Nineteenth Century. The painter, who never left France, found models for his canvases during visits to Paris’s Museum of Natural History, the zoo and botanical gardens, as well as numerous colonial expositions. He also culled images from books, magazines and postcards.

In one of his first, typically enigmatic forest pictures, Rousseau painted a moonlit, costumed couple strolling by a house decorated with a lantern and a mask. “Carnival Evening,” 1886, attracted little attention at the artist’s first public exhibition, the Salon des Indépendants of the same year, but has since been recognized as one of his finest early works. Courtesy of Philadelphia Museum of Art.

These sources stimulated colorful, vibrant, challenging, often enigmatic canvases that brought Rousseau recognition in his time and established his later fame. Each has a special vitality and mood. The very strangeness of these exotic pictures ensures their enduring appeal.

The artist’s first foray into jungle work, “Tiger in a Tropical Storm (Surprised!),” 1891, shows the ferocious-looking animal prowling through rain-pelted, lush undergrowth. The beast ready to pounce may have been inspired by Eugene Delacroix’s midcentury images of tigers on the verge of combat. Although critically acclaimed by some, Rousseau did not revisit the theme for more than a decade, perhaps concluding that landscapes and portraits were more reliable means of generating income.

In the final half-dozen years of his life, Rousseau returned to jungle themes. Some of these disturbing dreamscapes reflect the savagery of the law of the jungle in graphic, bloody terms.

As Rousseau described, with disarming literalness, in “The Hungry Lion Throws itself on the Antelope,” 1905, “The lion, being hungry, hurls itself on the antelope, [and] devours it; the panther anxiously awaits the moment when she, too, will have her turn. Carnivorous birds have each torn off a piece of flesh from…the poor animal as it lets fall a tear! Sunset.” The sensation “The Hungry Lion” caused at the Salon of 1905 encouraged Rousseau to create other views of jungle combat.

Enormous bunches of bananas, along with myriad other forms of flora, form the backdrop for the depiction of a tiger chomping on his fallen prey in “Fight between a Tiger and a Buffalo,” 1908. Rousseau also painted a jaguar attacking a horse, a lion devouring a tiger and even an American Indian grappling with a gorilla.

In a lighter vein, in several canvases Rousseau showed almost-civilized, quasi-human monkeys amidst luxuriant greenery. In “The Merry Jesters,” 1906, the two monkeys improbably playing with a milk bottle and back scratcher are nearly engulfed in tropical vegetation. The monkeys peering at the viewer through the undergrowth in “The Equatorial Jungle,” 1909, “Monkeys in the Jungle,” 1910, and “Tropical Forest with Monkeys,” 1910 (showing two primates fishing, like men in his suburban landscapes), display human characteristics.

Unfortunately missing from the exhibition is “The Sleeping Gypsy,” 1897, the familiar, fantastic and puzzling depiction of a peaceful, bug-eyed lion nuzzling an exotic woman lying next to her guitar in an expansive, barren landscape. Its owner, The Museum of Modern Art, felt it could only loan one of its two popular Rousseaus, and the organizers chose “The Dream.”

Although he was an untrained outsider, Rousseau was admired by avant-garde artists and liked to dress the part of a contemporary painter, as shown in this photograph in his Paris studio in 1907. Courtesy of Archives Larousse, Paris, France/The Bridgeman Art Library.

“The Sleeping Gypsy” and “Eve,” circa 1906-07, set the stage for the culminating work of the artist’s career, the unforgettable “The Dream” of 1910. In the Gauguin-like “Eve,” Rousseau recorded the moment when the heroine, standing in a tropical forest, takes the forbidden fruit from the snake.

“The Dream,” painted in the last year of Rousseau’s life, summarizes the qualities that make his art unique. Masterfully using color and form in an intriguing composition, he melded the moonlight of “Carnival Evening,” the exotic foliage of his jungle pictures, the nude of “Eve” and set the voluptuous figure of an early lover on a red sofa amid lush vegetation. Crowded into the dense jungle are an exotic snake charmer, birds, an elephant, and wide-eyed lions peering at the viewer. It is a fascinating image; little wonder modernist pioneers and Surrealists found it compelling.

Soon after completing “The Dream” Rousseau died, destitute, at age 66, of blood poisoning. Eventually, longtime admirers Delaunay and Picasso arranged to have his remains crowned by a tombstone carved by Constantin Brancusi and placed in a cemetery in his birthplace of Laval.

In a quarter century of painting, the humble, self-taught former customs agent established a unique niche in art history. As French art critic Jean Bouret once wrote, “He created a paradise beyond his reach, yet he filled it with ordinary people – his world was that of the red plush sofa in the middle of a tropical forest.”

This splendid exhibition, showcasing the range and depth of Rousseau’s unique vision and idiosyncratic style, confirms the artist’s standing as an outstanding aesthetic innovator, keen observer of the Paris of his day and enduringly captivating, naïve painter. It justifies Tate Modern director Vincente Todoli’s assertion that “Henri Rousseau remains one of the most popular artists of all time.” The 230-page, illustrated catalog, published by Tate Publishing, includes essays by British and French scholars surveying Rousseau’s career and offering insights into his sources and the meanings and messages of his paintings. It sells for $50 hardcover and $35 softcover.

A full program of related lectures and other activities is scheduled. The National Gallery is on the National Mall between 3rd and 9th Streets at Constitution Avenue NW. For information, 202-737-4215 or www.nga.gov.