This striking likeness of an intense, red-haired young man, “Portrait of a Man,†circa 1815, may be a self-portrait of Norwich evangelist Harlan Page (1791‱854). Painted around a year after he was “born again,†it suggests someone filled with religious fervor. Gift of HSB.

It is rare when the acquisition of a single collection of artworks transforms an established museum’s outlook and mission. Yet that, fortuitously, is what has happened at the beloved Florence Griswold Museum, long heralded as the home of American Impressionism.

In 2001, the historic 1817 house museum, where talented turn-of-the-century Impressionists flourished under the benign eye of kindhearted landlady Miss Florence Griswold, received 190 works of art from the Hartford Steam Boiler Inspection and Insurance Company (HSB) of Hartford, Conn. Comprising Eighteenth to Twentieth Century American paintings, prints and sculpture, the highly regarded collection concentrated on Connecticut’s artistic heritage.

This copious blessing has changed the Griswold from a National Historic Landmark house museum focused on art of the Lyme Art Colony to an expanded institution whose mission encompasses American art. According to Smithsonian American Art Museum director Elizabeth Broun, the donation of HSB’s art holdings, “truly one of America’s landmark collections, is the kind that can put a museum on the map.”

Longtime Griswold Museum director Jeffrey Andersen agrees, observing that the gift of the HSB Collection “charted the course for the museum’s growth from a respected house museum to a true American art destination.” It now offers visitors, he adds, “a compelling experience that combines [American] art, history and landscape.”

Celebrating the tenth anniversary of HSB’s remarkable donation, “Inspiration and Impact: The Legacy of the Hartford Steam Boiler Collection,” on view through June 26, pairs standouts from the HSB trove with three dozen recent acquisitions reflecting the museum’s enlarged focus. Some additions in the past decade build on strengths of the HSB Collection’s fine examples of American Impressionist landscapes, while others document achievements of lesser-known Connecticut artists, boost the museum’s commitment to women artists and introduce modern artists of the late Twentieth and early Twenty-First Centuries.

In this interesting double likeness, French-trained Robert Vonnoh (1858‱933) painted “Portrait of Bessie Potter Vonnoh,†his diminutive sculptor-wife (1872‱955), in 1907 as she worked on her sculpture of actress Julia Marlowe. The painter appears in the mirror behind. Prominent artists in their day, the Vonnohs had a home and studios in Lyme’s “Pleasant Valley.†Museum purchase.

The exhibition is showcased in the museum’s Krieble Gallery, which provides ample space for displaying large exhibitions such as this. Also on the 11-acre museum site overlooking the Lieutenant River are education and landscape centers, expansive gardens and the restored studio of Old Lyme painter William Chadwick.

A dramatic testimonial to the transformative effect of the HSB’s donation is in the field of American Impressionism. Although the Griswold is a key site in the evolution of that style, it owned only one canvas by its leader and most enduring star, Childe Hassam.

Thanks to HSB, the museum now boasts eight substantial Hassam works, ranging from “Summer Evening,” 1886, showing a woman in white seated at a window on Appledore Island in the Isles of Shoals, to a gloriously high-keyed evocation of autumn in “The Ledges, October in Old Lyme, Connecticut,” 1907. Hassam, whose example changed the art colony’s dominant style from Tonalism to Impressionism, had a special studio of his own near the banks of the river. “You should see [my studio] here,” he wrote J. Alden Weir in 1906, “just the place for high thinking and low living.” The site of the studio remains clearly visible.

The museum has also added works by Weir and other key Impressionists like Willard Metcalf, Theodore Robinson and John H. Twachtman.

Reaching further back in the HSB holdings and broadening the museum’s scope is a grand portrait by Ralph Earl, a frequent Connecticut resident, of a strong-willed lady of the early republic and significant paintings by Hudson River School stalwarts Thomas Cole and Hartford-born Frederic Church. The latter’s oil painting of the famed Charter Oak near Hartford, painted while in his early twenties, evokes a dramatic incident in the state’s history.

One of the most compelling canvases recently purchased by the museum, “Farmer Roscoe,†circa 1937, by Russian-born Ivan Olinsky (1878‱962), was reworked considerably into its present form. Olinsky said his depiction of this Lyme farmer “suggests man’s attitude toward life and the soil.†Museum purchase.

Church’s early masterpiece is linked in the exhibition to contemporary counterparts †evocative photographs of venerable New England trees from the 1990s “Portraits of Trees” portfolio of Connecticut-based Tom Zetterstrom. “These connections,” observes curator Amy Kurtz Lansing, “provide a broader context for the HBS works. The pairings initiate new dialogues with favorites from the collection.”

Celebration of Connecticut’s landscape remains the nucleus of the museum’s holdings †and at the heart of its acquisition program.

Wonderful discoveries of virtually unknown, but accomplished Connecticut artists are epitomized by the purchase of four captivating pastel portraits of members of the strait-laced Noyes family, who resided along Lyme Street near the Griswold. Dating to around 1798, they were painted by British-born James Martin.

The Noyes paintings complement a powerful, primitive likeness, perhaps a self-portrait, painted about 1815 by fervent evangelist Harlan Page of Norwich, from the HSB Collection. Page’s fervor is palpable; as longtime museum shop manager Lois Bordner, who counts it among her favorites, puts it, “The wild-haired man&⁩s portrayed so full of passion that it looks as if his head might burst into flames.”

A typically superb still life, “Peonies in a Vase,” circa 1885, by African American Charles Ethan Porter of Rockville, himself newly visible on the national art scene, came from HSB. His work is joined by recent Nutmeg State artists like James Britton, Barbara Eckhardt Goodwin and Abram Poole, whose works have been added through gifts from private collectors.

A major recent purchase, Willard Metcalf’s beautiful oil “Kalmia,†1905, depicts pink and white blossoms of the mountain laurel, Connecticut’s state flower, that bloom along the Lieutenant River adjacent to the Griswold property. A New Englander whose special feel for its landscape translated into a large oeuvre of endearing images, Metcalf’s “Kalmia†will be the centerpiece of an exhibition on the theme of laurel opening in the gallery on May 6. Museum purchase through the Nancy Krieble Acquisition Fund with the support of numerous funds and individuals.

A good example of how HSB’s beneficence built on the Griswold’s strengths is the work of gifted Impressionist Willard Metcalf, whose darkish 1880s view of a North African scene contrasts with the brilliant hues of a masterwork, “Kalmia,” painted nearly 20 years later, and purchased by the museum recently. The Griswold is now the largest public repository of Metcalf’s oeuvre.

Also complementing HSB acquisitions are a “Self Portrait” and a likeness of his wife, sculptor Bessie Potter Vonnoh, by Robert Vonnoh, and Ivan Olinsky’s striking, strong portrait of an Old Lyme farmer.

As a result of a sustained effort over the past decade, the Griswold has augmented its holdings of women artists, notably through the gift of a charming portrait of a young woman by Cecelia Beaux, arguably America’s finest female painter who made her career in this country. (Mary Cassatt was an expatriate in France.) “Awakening Diana,” 1960, a classically modeled bronze by Elisabeth Gordon Chandler, reflects the sculptor’s commitment to traditional techniques of academic art, which led her to found the respected Lyme Academy of Fine Art, which donated the work.

Among the seven paintings by Childe Hassam in the HSB Collection was “Summer Evening,†1886, invoking a frequent theme of a woman near a window. In this case, the setting is Appledore Island among the Isles of Shoals, off the Maine-New Hampshire coast, where the popular Impressionist created some of his best pictures. Gift of HSB.

Some of the best folk artworks in the collection, thanks to HSB, are endearing, miniature, watercolor portraits of the Richards family of New London, created around 1790 by their townsman, Mary Way (1769‱833). They complement the Earl painting of Mrs Guy Richards a few years later.

Since the HSB gift encompassed primarily Connecticut art into the early Twentieth Century, the Griswold has been rounding out its collection by acquiring mid-to-late-Twentieth Century works by such Nutmeg State artists as James Grunbaum, Norman Ives and Sewell Sillman. The donation of some 30 pieces by the latter’s family foundation has made the museum a center for the study of Sillman’s oeuvre.

In addition to broadening its scope as a result of the HSB gift, the Griswold continues to acquire works associated with Miss Florence and the Lyme Art Colony. In addition to Metcalf’s “Kalmia,” the museum in the last decade has added works by art colony stalwarts George M. Bruestle, Charles Ebert, Edmund Greacen, Henry Rankin Poore, Henry Ward Ranger, Edward C. Volkert and Henry C. White.

Standouts among recent acquisitions are George Bogert’s dark but glowing view of Venice just after sunset, Wilson Irvine’s sunlit winter landscape and Edward Rook’s radiant evocation of his first house in Old Lyme. They enhance appreciation for the achievements of the Lyme Art Colony and remind visitors of the great debt owed to the incomparable Miss Florence, who nurtured so many talents under her roof and left her majestic home as an important repository of America’s national artistic legacy.

Lillian Westcott Hale (1880‱865), who was born in Hartford and had the good fortune to marry a fellow artist, Philip Hale, who encouraged her work, specialized in warm and intimate domestic scenes. “Woman Resting,†circa 1920, shows her daughter asleep in a careful composition marked by brightly hued bed coverings. Gift of HSB.

Long a pilgrimage for lovers of American Impressionism, the Florence Griswold Museum used to be well worth a visit just to see the dining room, ringed with wall panels and doors painted by members of the Lyme Art Colony. The house has recently been restored to its look in its heyday around 1910, and the dining room remains one of the great rooms of America.

Now that the museum’s trove of art colony painters has been augmented with the HSB’s magnificent treasures, broadening the historic house’s mission, it has become a must-see East Coast/New England art site.

There is no catalog for “Inspiration and Impact,” but The American Artist in Connecticut: The Legacy of the Hartford Steam Boiler Collection , written by Griswold director Andersen and state art authority Hildegard Cummings, serves that purpose. It illustrates highlights and offers rewarding and revelatory insights into the trove. Published on the occasion of the debut of the HSB gifts in 2002, the 143-page book sells for $29.95, softcover.

The Florence Griswold Museum is at 96 Lyme Street. For general information, www.florencegriswoldmuseum.org or 860-434-5542.