Judy Knudsen, manager of the Center for Local History at the Arlington's Central Library, looks through a drawer of train and trolley route maps. (John Kelly/The Washington Post)

There is no dictionary definition of “the Arlington way,” but this is pretty close: Decisions that will affect the community are made only after input from all the voices in the community.

Now, depending on the ultimate decision, Arlingtonians may feel that this is wonderfully democratic or needlessly complicated. But what is undeniably true is that Arlington’s many constituencies like using their voices.

And that’s good for the Center for Local History, a repository for many of those voices. The center is in the county’s Central Library on Quincy Street. The operation used to be known as the Virginia Room, the name given to many library-based local history collections throughout the commonwealth. The name was changed two years ago to reflect the fact that its focus is so local. Yes, there are books on Virginia history and some genealogical materials, but if you’re doing a deep dive on your family, the small staff will suggest other places to do your research.

This is a place to luxuriate in unadulterated Arlingtonness, from the suburbia of Dominion Hills to the fleshpots of Rosslyn. Well, the former fleshpots. Before about 1910, when a crusading district attorney turned things around, Rosslyn was known for its bars, brothels and gambling dens.

“We always fight the idea that Arlington started in 1920,” said Judy Knudsen, the center’s manager. That was the year the name “Arlington County” came into being. Before then, it had been part of Alexandria County. And before that — until the retrocession of 1847 — it had been part of Washington. In 1920, the urban and urbane residents of Alexandria severed their ties to the rest of the county, having decided that they didn’t want their fortunes connected to rural Arlington.

From left: John Stanton, Eugene De La Rosa, Heather Crocetto and Judy Knudsen at the Center for Local History in Arlington. They help preserve the history of the Virginia county. (John Kelly/The Washington Post)

It’s hard to tell whether Arlington’s feelings are still hurt. Probably not, given how civic-minded many of today’s Arlingtonians are.

“People in Arlington are very neighborhood-centric,” Judy said. “They’re passionate about their neighborhoods.”

That’s reflected in the community association newsletters in the Center for Local History’s collection. Here are played out conversations about speed bumps and playgrounds. The center also has records of two local garden clubs — Rock Springs and Glencarlyn — and is the official repository of the school board archives.

One of the most-consulted collections is a set of residential and commercial building permits from 1935 up to the early 1980s. John Stanton, research associate, has mastered the arcane index to the microfilm, which sits in a box bristling with Post-its and handwritten notes.

The center has thousands of photographs, too, including hundreds taken by a man named Jim Palmer, who in the 1990s started shooting every church, school, library and shopping center in the county. That wasn’t really all that long ago — and the black-and-white photos are plain — but in a place that changes as rapidly as Arlington, they are literal snapshots of a point in time.

Heather Crocetto, archivist, is processing the records of Fred Sheridan, an architect who worked in and around the county for six decades. The center also has the records of Signature Theatre, whose humble Arlington roots have spread all the way to Broadway. (One of the odder requests Heather received: The Manhattan DA needed to see whether a suspect was really at rehearsal on a particular day, as he maintained in his alibi.)

Eugene De La Rosa, the center’s digital archives specialist, is helping the collection live online. Already, there are interesting highlights, including colorful posters created around 1970 by Wakefield High School students.

And there are the voices. The center has compiled some 400 oral histories. Dozens were collected for the fifth anniversary of Sept. 11, 2001, including one with Arlington County fire chief James Schwartz. (One of the challenges he described: keeping well-meaning Pentagon personnel from going back into the burning building in search of colleagues.)

One of the most delightful conversations was with William H. Pelham Sr., whose grandfather Moses Pelham founded what became known as Pelham Town, a community of black homeowners at what is today 24th and Wakefield streets. It was conducted in 1986, when William was 86. He speaks of a vanished time, of slaughtering hogs on Thanksgiving morning (a chore he hated) and working in a quarry on the Potomac. His memories include how the men from his church, Mount Salvation Baptist, would dam up a branch of Spout Run so water would pool and create a setting for baptizing new converts.

If you’ve been metaphorically baptized in Arlington, with a long history in the county, the center may want to talk to you, too.

Twitter: @johnkelly

The Center for Local History is open 10 to 5 on Mondays, Tuesdays, Thursdays and Saturdays and 1 to 9 on Wednesdays. It’s in the Central Library, 1015 N. Quincy St., Arlington. Since much of the material is stored off-site, it’s best to e-mail or call ahead. Visit library.arlingtonva.us/center-for-local-history or call 703-228-5966.

For previous columns, visit washingtonpost.com/johnkelly.