Twins Ruth, left, and Rebecca Brown have made Civil War-themed dioramas using tiny clay cats since they were in their teens. In September, they opened the Civil War Tails at the Homestead Diorama Museum in Gettysburg, Pa. (Matt Roth/For The Washington Post)

In September, in the shadow of the historic battlefield here, twins Rebecca and Ruth Brown opened Civil War Tails, possibly America’s most whimsical war museum.

Their collection of scale-model battle dioramas includes Fort Sumter, the Battle of the Ironclads and their masterpiece, four years in the making, Pickett’s Charge, 1,900 cat soldiers in all.

Yes, cats, an inch or smaller, each one lovingly sculpted in clay by the 32-year-old sisters, then baked in a 225-degree oven. The choice of figurine was born of necessity more than devotion, although the sisters like cats plenty. “We just don’t make clay people as well as cats,” Rebecca says.

But they were determined to have a museum. It had been their dream since they were suburban Philadelphia middle-schoolers and fell in love with history and the War Between the States. They imagined a time when they could open a museum in Gettysburg to share their passion with others.

Their museum is certainly unique, but in the desire to create it, they are far from alone.

America is often depicted as a buffet of fast food and disposable culture, the shiny and new. But this is also a nation besotted with history, collecting — and museums.

We have far more museums than other countries, somewhere between 28,000 and 35,000, depending on which museum organization is counting. (Most likely, we have more museum organizations, too.) This is more than double the number since the 1990s, according to the Institute of Museum and Library Services.

And the list doesn’t include the opening last year of the Broad museum in Los Angeles, the new Whitney in Manhattan, and Ralph Nader’s American Museum of Tort Law (because, apparently, we didn’t have one yet) in Winsted, Conn.

This year is like the Museum of the Month Club.

The Met Breuer opened in March in the former Whitney. Last month, the National Blues Museum blew into St. Louis. Come fall, Washington, with its mall of museums, will add the Smithsonian Institution’s National Museum of African American History and Culture, a dozen years in the planning.

But our museumphoria is not fueled solely by the prosperous and the powerful.

In the land of opportunity, anyone can become a curator, and any home a gallery.

For every Met Breuer, there’s an institution like the Kansas Barbed Wire Museum . An East Harlem garbage depot is home to the Treasures in the Trash collection, 50,000 found objects — Tamagochis, Furbies, 8-track tapes — curated by New York sanitation engineer Nelson Molina. Off the coast of Maine, patrons can visit the Umbrella Cover Museum. Not the umbrellas, just the covers.

Every president has a museum. William Henry Harrison, president for precisely one month, has two: the presidential site in Indianapolis and Grouseland, his home in Vincennes, Ind., when he was governor of the territory. Elvis has Graceland; Harrison his Grouseland.

There is, it seems, a museum for everything. And also a Museum of Everything. Literally. Based in Britain with a branch in Rotterdam and pop-up installations throughout Europe. (Volunteered to visit. Boss: Uh, no.)

What’s behind this exhibitionistic zeal? Not to get too esoteric, but we are a nation that excels at saving stuff.

“The growth in museums,” says Marjorie Schwarzer, who teaches museum studies at the University of San Francisco, “comes from nostalgia, nerds and natural collectors. Most people can’t collect a Renoir, but they can collect old hammers.”

Indeed, there is a Hammer Museum — not to be confused with L.A.’s Armand Hammer Museum — in southeast Alaska.

“People amass all this stuff,” Schwarzer says, “and where are they going to put it?”

Most museums fall into one of two categories, says Elizabeth Merritt of the American Alliance of Museums. She is the originator of the theory of omphalic museum classification or, in the vernacular, “How Museums are Like Belly Buttons,” a post she wrote for the website of the Center for the Future of Museums, of which she is a vice president.

“Outies,” she notes, “feed a need in the community, like children’s museums.” There has been a bonanza of children’s museums since baby boomers started breeding and looking for ways to stimulate their wee ones intellectually, while avoiding being dragged to the 232nd Pokemon movie.

“Innies,” Merritt writes, are “often created by enthusiasts who are sure that other people will appreciate their passion once it is shared in the form of a museum.”

Schwarzer labels these “foamer museums,” as in foaming at the mouth in their enthusiasm.

Among her favorites is the Umbrella Cover Museum on Maine’s Peaks Island, which has a collection of 730 and counting. She is fond of the mission statement by founder Nancy 3. Hoffman, the digit not a typo: “The Umbrella Cover Museum is dedicated to the appreciation of the mundane in everyday life. It is about finding wonder and beauty in the simplest of things, and about knowing that there is always a story behind the cover.”

Civil War Tails is a pronounced Innie, based on the twins’ indefatigable zeal for the Civil War and their total recall of intricate military strategy and the lengthy biographies of countless cats, er, officers and infantrymen.

“We want to reach the younger generation,” says Ruth, a lawyer by day. Rebecca works as a waitress at a nearby hotel restaurant so she can man the museum. “If they don’t get the history bug, they’ll get the art bug.”

Or, failing that, “We’ll get the crazy cat people.”

In the mid-19th century, America was home to few museums. The Smithsonian opened in 1855, launched by a British scientist’s collection.

The museum building boom started in the late 19th century — New York’s Metropolitan Museum of Art was founded in 1870, the Art Institute of Chicago nine years later — and was a byproduct of the robber barons’ generosity and ego, a gift of gilt for the multitudes.

Tax laws favor rich folks transforming their private collections and their homes into charitable exercises, but deep pockets aren’t necessary to open a museum.

The Brown sisters created their collection at minimal cost, through years of effort, beginning at age 13. So far, they’ve completed 50 dioramas.

With family help, they bought a former girls’ orphanage dormitory in Gettysburg, where they live above the two-room museum. The required annual amusement license is $50.

Their largest expenses were making the building wheelchair-accessible and buying souvenirs (T-shirts, display domes for model cats) for the gift shelf.

Building an audience, however, can take time.

In February, the Browns hosted 45 adults (tickets $6.50) and 10 kids ($5). There were days when no one visited. The sisters will not get rich on this project, but they’re doing something they love.

The growth in museums is unlikely to stop, although a few do close, such as Washington’s Corcoran Gallery of Art and the National Museum of Crime and Punishment.

Some regional institutions in areas hard hit by the 2008 financial crisis, such as the Fresno Metropolitan Museum of Art & Science, have been shuttered because of a lack of funding. And small museums, “Innies” founded by “foamers,” close because of limited interest or the creators’ inability to continue.

In general, however, “we’re only going to have more” museums, Schwarzer says. As the baby boomers age, where is their stuff going to go?

“There’s the food truck phenomenon of museums,” she says, meaning not literally trucks — although, who knows, there may be some — but that anyone with enough pluck and enthusiasm can start a museum. “We have more stuff, the entrepreneurial drive and the freedom to play around.”

Despite the quiet winter, the Browns remain undaunted.

They hope that the summer, with the July anniversary of the battle, will bloom with visitors.

The sisters are working on the latest diorama, the Battle of Little Round Top, the second day of Gettysburg.

Rebecca creates Confederate soldiers, while Ruth constructs the Union forces.

One thousand cats made; 4,000 to go.