Created by architects Tod Williams Billie Tsien and Associates, the building is a mere five stories high, only two town houses in width and one of the best museum structures anywhere.

The exciting façade is made of angled panels of tombasil, a silvery-gold alloy of bronze more commonly used to make boat propellers. Two-thirds of the panels are smooth, but one-third are roughened and provide shimmer to the building's canted face.

The entryway leads to a two-story lobby filled with natural illumination from a skylight high above. Through this well of sunshine, a small amount of light filters into every floor of the museum.

The walls are simple concrete; the floors, warm, light wood with surrounds of ground concrete. The walls of outer stairwells contain niches to spotlight individual objects, while inner stairways of various sizes slice the airy interior into inviting smaller areas to explore. Pale green fiberglass panels along one stairway add a touch of color. Wooden benches allow visitors to rest and savor the often-soaring vertical but human-scaled horizontal spaces.

After 40 years of searching for a permanent home, the museum has at last built its own -- simple in feel yet complex in organization, fresh and dignified. It's the perfect showplace for its ever-growing collections.

Besides the five compact floors above street level, the museum has two lower floors -- the first sub-street level contains a coat check, auditorium and classroom, the lower has a library, rare book room and offices. All this for $22 million!

Only the café on the second floor and the bookstore near the entrance seem a tad tiny. They may be fine for now, but I predict the museum will prove so popular that both areas will be outgrown quickly.

The museum is celebrating with two surveys of its permanent collection, entitled "American Anthem." Part one consists of "American Radiance: The Ralph Esmerian Gift to the American Folk Art Museum" (through June 2, 2002) and "Darger: The Henry Darger Collection at the American Folk Art Museum" (through June 23, 2002). Part two will feature "Masterworks from the Permanent Collection" in a chronological arrangement starting next July.

The Darger material is part of the largest archive of work by Chicago's most famous "Outsider artist," Henry Darger (1892-1973). This self-taught loner produced the world's longest and one of its strangest novels, then illustrated it with delicately tinted mural-size watercolors. "Darger" consists of books, source materials and 26 mostly double-sided nine-foot-long long drawings that illustrate his 15,000-page In the Realms of the Unreal. The exhibition takes up the second floor of the new building and was organized by Brooke Davis Anderson of the museum's Contemporary Center.

The top three floors and entry level are filled with more than 400 mostly 18th- and 19th-century pieces from the Ralph Esmerian Collection. Esmerian, chairman of the museum's board of trustees, has one of the finest collections of Pennsylvania German material. This show presents his collection as one of outstanding depth and surprising breadth. From early portraits by John Durand and Reuben Moulthrop, the collection goes on to fraktur (embellished texts often with German Gothic lettering -- birth and baptismal records, religious verses, love tokens, bookplates and tunebooks), then on to folk pottery and furniture, weathervanes, scrimshaw (decorative whale bone and tooth carving), Shaker pieces, weathervanes, genre paintings and school-girl needlework. All are broadly represented.

One of the iconic paintings of American folk art is Esmerian's Girl with Red Dress with Cat and Dog (ca. 1830-35) by Ammi Philllips. That oil greets visitors on the first floor. Other outstanding portraits include a wall of faces by the well-known itinerant New England watercolorists Samuel Addison Shute and Ruth Whittier Shute. Across from them are even better portraits of a mother, father and daughter by the Carver Limner from Freeport, Me. The visages are enlivened with so many bold and sweeping patterns that the result is graphic dynamite.

Three of Esmerian's 20 pieces of painted furniture by the Virginia artist Johannes Spitler (1774-1837) are on display, including a wonderful blue tall-case clock with white and red designs. Esmerian's collecting led to the identification of the artist and proof that Germanic and Swiss furniture makers were influenced by fraktur.

Stacy C. Hollander, senior curator, organized the Esmerian show and its catalogue, a huge, beautiful, door-stop of a book by Harry N. Abrams ($75, hardback).

Go see New York's latest treasure. The American Folk Art Museum is open every day, except Monday, from 10 to 6 p.m., Fridays to 8 p.m. Admission is $9; students and seniors $5. Free admission on Fridays, 6-8 p.m.