CAMPBELL — With its quirky front entrance — flanked by two painted missiles — that leads to a trove of grenade vests, canteens and more, The Mountain View military surplus store already stands apart from the competition.

In its 40 years on Bascom Avenue, the longtime Campbell institution has resisted the pressure to modernize like other surplus shops that have shifted to selling more brand-name clothing and commercial goods. True to its roots, The Mountain View primarily sells military-issue items.

But now other forces of the modern age are catching up with the store, which is holding a half-off-all-items sale before shutting its doors July 15. A confluence of events — the rise of online retailers, looming property redevelopment and crippling Bay Area rent prices that make it nearly impossible to profitably relocate — have convinced Roger and Crystal Bonner, The Mountain View’s owners, to retire their business for good.

“I’m of the belief you can’t make it brick and mortar anymore,” Roger said. He currently sells World War II and Vietnam War collectibles on eBay and plans to continue that after the store closes.

The Bonner family’s surplus business launched in 1947, when Roger’s father, David, opened a store in El Cerrito. By the time David Bonner opened the Campbell store in 1976, it was the fourth in a chain.

Roger, 66, said surplus stores, ubiquitous when he was growing up in the 1950s and ’60s, have grown rarer over the years. A smattering remain, but he still counts his shop among a handful left in the Bay Area.

And even within the world of surplus, The Mountain View is unusual. Roger estimates that 80 percent of the items in his store are still military-themed, while other similar stores have gone, in 67-year-old Crystal’s words, “REI mainstream” — branching out into other products as post-World War II military-issue materials became increasingly difficult to find.

Up until the 1990s, the Bonners bid on auction items at military bases — now closed — in Mountain View, Alameda, Monterey and Stockton. They turned to European surplus in cases where American items were scarce.

“We felt we could make a living and be different than the others,” Roger said. “We wanted to keep that uniqueness even though we realized that meant we were not appealing to the mass market.”

The Bonners’ inventory appeals greatly to enthusiasts of authentic gear, as well as customers looking for well-made goods. The government has stringent regulations for its military manufacturers, and the Bonners say military-issue is synonymous with high quality. Customers agreed.

“It lasts longer than what you’re going to get at Big 5 or Walmart,” said Los Gatos resident Stephen Jester, who popped into The Mountain View for the first time last week to check out the sale.

Longtime customers who turned out for the sale said they will miss the Campbell institution’s unique inventory and vibe that Roger says makes many visitors feel like “kids in a candy store.”

“It has a really nice nostalgia to it,” said Reza Hariri, who used to visit the store mostly for Halloween costumes.

Despite this, Keith May, who has worked at The Mountain View since 1997, said it’s been hard to watch interest in the store’s wares wane in recent years. May attributed the decline to a general decrease in enthusiasm for war items. But the Bonners say there is another culprit: the internet.

Online services such as Amazon and eBay have cut into their already highly niche market, and Roger estimates that over the past eight or nine years his store’s sales have gone down at least 20 percent as a result. The Mountain View’s dilemma is common among small businesses dealing in hard goods, he said.

The Bonners tried to adapt with a store website, but ultimately it was too costly to maintain the site and to keep up with frequently changed regulations from services like Google Shopping.

But a changing sales landscape was just one factor in the Bonners’ decision to close. For about a decade now, they have rented their store’s land on a month-to-month lease with the knowledge that their landlords — descendants of the family that owned the site when the Bonners first moved in — wanted to eventually redevelop. Then, in January, the terms of the Bonners’ contract changed to guarantee only 30 days notice before they had to move out.

Moving out on such short notice “would kill us,” Roger said. Unwilling to deal with that added uncertainty, the Bonners decided to close on their own terms and set a date.

Florence Sordello — who owns interest in E. Barbanos Enterprises, which holds the Bonners’ property — confirmed plans to redevelop multiple Campbell properties. Either way, Sordello said, the Bonners were considering retiring.

Roger does not blame the landlords and said he is appreciative of his store’s 40-year stay. He and his wife decided that, given Silicon Valley’s ever-increasing property prices — their own rent is eight times higher than it was when they moved in — they will not try to reopen elsewhere.

The Bonners, however, have been heartened by their customers’ response to the closure. “They tell me there’s not another store like us anywhere in the area,” Roger said. “That’s the highest compliment I could get.”

Contact Hannah Knowles at 408-920-5767. Follow her at Twitter.com/KnowlesHannah.