The showmobile is now an old mobile.

Dating to the 1960s and '70s, the bandwagon trucks are rusting away after decades of being the stage for summer plays, municipal park concerts and the soapboxes for politicians out on the stump.

Town leaders say the trucks -- which can cost more than $150,000 to replace -- are essential to life on Long Island, particularly in the summer at beaches and parks, when local show business reigns over hot, humid nights.

Showmobiles generate revenue, but also are appreciated by residents and summer camp directors because not every community has a stand-alone stage in a public park. This makes the bandwagon brought to the park on the back of a truck a small-town essential.

"They are the symbol of small-town living: the community bandshell, the town green, where neighbors meet up, and people got their entertainment," said Judi Bosworth, supervisor of North Hempstead Town, where officials have allocated funds to replace one from 1987 and another from 1978. "It was never a thought about not replacing these."

Oyster Bay has a new $154,000 showmobile arriving this summer. Some towns in recent years have replaced or added to their fleets, and officials in others say they are considering buying new ones.

Towns that don't have bandshells or concert venues rely on trucks as the "regular theater on wheels," Jill Weber, North Hempstead's parks commissioner, said. "As long as the truck fits and the funding is available, they can go wherever you need them."

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North Hempstead, with 833 acres of parkland, beaches and gardens, sees demand, for events such as fireworks shows and ethnic parades.

The town, with roughly 225,000 residents and 70 square miles, can spread out the scheduling. Showmobiles "offer people an opportunity in every neighborhood park," Weber said. More than 80 groups -- 30 from outside the town -- rented the showmobile in 2014, providing a total of $21,000 in revenue.

The town's three showmobile trucks are stored by the beach in Port Washington over the winter. They are dilapidated and replacing them is cheaper than upgrading parts.

The new 36-foot vehicle in Oyster Bay is the town's fifth. Huntington has one. Hempstead Town controls seven. Nassau County has six.

Decades after making their first purchases, some towns still reserve funds in their capital budgets in the hopes of buying new vehicles. Costs have risen. For example, Oyster Bay paid $60,000 for a 28-footer in 1995.

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"They really are symbols of suburban living," Oyster Bay Supervisor John Venditto said. The town does not charge rental fees and generates no revenue from the trucks, said Venditto, who called them "iconic."

The five trucks in Oyster Bay "are the most we've ever had," Venditto said. "At certain times of the year, the demand definitely exceeds the supply, to the point where we call other municipalities, and they call on us," Venditto said.

In Babylon, a vehicle used by the town's beach to stage a concert "became an instant hit" and officials wondered "why don't we build a permanent structure there?" recalled Frank Bachety, the town's parks commissioner. Officials in 2008 seized on the demand and built the town's first bandshell.

The first showmobile truck was built in 1959, according to Chris Storjohann, a sales representative for Wenger Corp. in Owatonna, Minnesota.

The company, which has sold about 1,000 since then, has contracts with New York City and in towns across the nation, including North Hempstead.

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It sent nearly two dozen showmobile stages to Vietnam during the war for Bob Hope's USO tour.

Trucks built in 1959 are still in use, including in Long Beach, California, and Cedar Rapids, Iowa, where the Long Beach Municipal Band and the Cedar Rapids Municipal Band play. Many from the 1970s are in use across the country, and sold and refurbished.

The technology has evolved. The first was designed with tiered risers for brass instrument bands, with the wings of the truck opened by cables and pulleys. Now, they are operated by hydraulics and remote controls.

Bob Uhl, president of Century Industries in Sellersburg, Indiana, said the company -- which sold its showmobiles to Oyster Bay -- began in 1979. Then, cities and towns nationwide had suffered from budget cuts. The company marketed the stages as a way to collect more revenue.

Politicians enjoy them, too. "They're used for every dedication, every ribbon cutting, every civic event, every political event," Uhl said.

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"As supervisor, I see people's reactions when they see the showmobile," Bosworth said. They include: "Something's going on here, what's happening, let's check this out."

On many vehicles, the names of town officials are listed and visible to the crowds.

For Bosworth, "When you're up there, it's part country fair, part Main Street USA rolled up into one." And she added, "it sure helps for people to see me when I'm up there on that showmobile stage, for someone of my petite stature."

In the months after superstorm Sandy, officials in the devastated City of Long Beach rushed to secure funding to rebuild. Billy Crystal, a Long Beach native, and his wife, Janice, had helped raise $1 million to the city, of which nearly $140,000 was used to buy the city's second bandwagon last year.

Councilwoman Eileen J. Goggin said adding that second vehicle "was just as important, in my opinion, to the infrastructure."

"People were so down," she said. "There was that fear -- forget about going to a concert -- whether or not I could live here or not, and whether the water would be working."

The funds were a relief for officials who had wanted a second vehicle but couldn't prioritize funding it.

"You need that other element to get the city going," she said.

A previous version of this story incorrectly reported the source of funding raised for Long Beach by comedian Billy Crystal.