Tom Dickinson is the first to admit that the photographs he’s been taking for nearly 40 years are not pretty.

“This is purely documentary photography, not art photography,” he said one evening last week at Westover Branch Library in Arlington, Va. “It’s photography with a message.”

That message: Arlington is disappearing. A certain kind of Arlington, anyway.

Several dozen of Tom’s photographs are on display at the library in an exhibit called “Windows to the Past: Arlington, Then and Now.” They are “before” and “after” photos of old Arlington homes — farmhouses, wooden bungalows, tidy brick Colonials, modest ranchers — and of the newly built mini-mansions that now stand in their place.

That title — “Windows to the Past” — is literal: The photographs are mounted in weathered window frames Tom salvaged from the old houses when they were torn down to make way for the new.

At last week’s opening reception, Tom delivered remarks as a slide presentation cycled on a screen behind him. These were Arlington houses in extremis. A lot of the photos were of houses just before they were torn down, after the last families to live there had moved out. There were backhoes in front yards, porta-potties, “No trespassing” signs, “Coming soon” signs.

“Everything you’re seeing here is gone, demolished, in a landfill,” said Tom, 67.

He started taking photos in 1980 after moving from Wisconsin to Arlington to work at the Pentagon as a civilian television producer. At the time, Shirlington was pretty much just one- and two-story buildings.

“We used to go to the deli,” someone in the audience said.

“The Grand Union was there,” said another.

Tom had never seen buildings demolished in Edgerton, Wis., the small town he grew up in. He couldn’t understand why anyone would tear down a perfectly good house.

But in Arlington — occasionally at first and then more and more frequently — he saw a life-cycle that goes like this: Buy a house for $500,000. Demolish it. Build to the maximum of the lot, then sell the new house for three times what you paid for the old one.

Tom and his wife, Ann, live in Arlington’s Bluemont neighborhood. He likes old things — he’s on the board of the Arlington Historical Society and is a past president — but his lament is for more than just the loss of old porches.

“We’re losing something in the character of the community, little by little,” he said. “It is progress in a sense, but there’s a price to pay.”

Part of that price is literal. This year, the average cost of a single-family home in Arlington went over $1 million.

“Who can afford that?” Tom asked. “You have to be a two-income family, like a doctor and a lawyer.”

Doctors and lawyers are nice, but do you want neighborhood after neighborhood of them? What’s happening to affordable housing? What’s happening to the environment when permeable land is built over?

Some of the demolished houses were historic, or interesting, anyway. One photo shows a Lustron home, those wacky, all-metal houses invented in the 1940s by a guy who used to work in a bomber factory. This one was dove gray, with jaunty red-white-and-blue awnings. In the next photo it’s a tangle of metal, like the wreck of the Hindenburg.

And finally there’s the modern house that took its place.

There’s a sameness to many of Arlington’s mini-mansions: an explosion of dormers, Craftsman-style columns, cathedral-ceilinged entryways, ocular windows, and out front: toothy, two-car garages.

“I just heard about a really beautiful Sears house on North Highland Street that was torn down in the last six months,” Tom said. “I went by and it’s just a hole in the ground.”

The exhibit — funded with a grant from the Arlington Arts program — will be up through Jan. 15. Tom is still taking photos.

Helping Hand

I have a confession to make: Until just now — right before I typed these words on Tuesday morning — I hadn’t made my donations to The Washington Post Helping Hand. But I just did it, and I can report that it’s so simple to go online and make a contribution to Bright Beginnings, N Street Village or So Others Might Eat.

Just visit posthelpinghand.com and look for the word “Donate.”

The three charities work with homeless families and adults in our area. Your gift will help.

Twitter: @johnkelly

For previous columns, visit washingtonpost.com/john-kelly.