New York (CNN) -- An average of $32 million a day in national parks revenue could be shut off if the Beltway showdown results in a government shutdown, officials say.
The measure would be the first shutdown in more than 15 years, shuttering national parks, seashores and historic sites, and barring some 800,000 daily visitors, according to David Barna, a spokesman for the National Parks Service.
Places such as Yellowstone National Park in Wyoming and Grand Canyon National Park in Arizona would be closed as a result of the impasse.
Tourist draws such as the Smithsonian National Museums in Washington would be locked and parades such as the National Cherry Blossom Festival could be called off, though organizers have pledged to hold a short parade despite the outcome. That festival draws roughly 1 million visitors each year.
Congressional lawmakers have been scrambling to negotiate a spending bill set to expire Friday, worrying those reliant on park tourism cash.
"These parks are the economic engines of some communities," said Barna. "They're often the largest employer in an area," referencing a network of restaurants, shops and hotels that often surround historic sites.
Barna, who says he remembers the last shutdown in 1995, says the potential loss of revenue could stymie local businesses.
"The biggest difference from '95 may be the affect on our website," he said.
The National Parks Service website tallies roughly 1 million daily hits, catering to would-be travelers and inquisitive students of history.
"It's the most popular website in the federal government," Barna said.
As part of the agency's contingency measures, it plans to post an out-of-service notice in place of the website.
Meanwhile, some 17,000 park service employees would be furloughed, with an additional 15,000 private contract workers also forced at least temporarily out of work.
The impasse's affect on tourism is perhaps most visible in Charleston, South Carolina, where Civil War re-enactors are descending.
For years, Charleston has been planning the commemoration of the 150th anniversary of the start of the American Civil War.
There, at Fort Sumter in Charleston Harbor, Confederate artillery opened fire on Union positions on April 12, 1861, igniting a bloody conflict that would last for the next fours years.
The Tuesday re-enactment of the bombardment is expected to take place regardless of the shutdown, with the firing of guns to take place outside federal land. But the hundreds of blue- or gray-clad re-enactors who planned to camp at the historic fort will find it locked in the event of a shutdown.
"We were expecting 2,000 visitors a day from now until Easter," said Fort Sumter Tours owner Rick Mosteller, whose company ferries boatloads of Civil War buffs out to the historic fort.
The effects, however, are also anticipated beyond Charleston Harbor.
"This is a tourist town," said city resident Robert Mikell. "A lot of businesses here rely on these national sites."
Farther to the north on Liberty Island in New York, the possible shutdown had already skewed the plans of some travelers.
"We started scheduling this week's vacation about four weeks ago," said Michigan resident Case Vaandering, who toured the Statue of Liberty on Thursday with his wife, Rochelle.
The pair said they had changed their route to visit the Smithsonian museums in Washington before venturing up to New York, fearful that a shutdown would block their favored Washington sites and museums.
"We thought the parks weren't going to open for us when we got here," Vaandering said.
Others remain more hopeful.
Kendra Barkoff, a spokeswoman for the U.S. Department of the Interior, said, "We still believe that there is the opportunity for Congress to avoid a government shutdown."
But the agency, like others around Washington, is also preparing "for all possible scenarios," she said.
In the event of a shutdown, all visitors and nonessential employees at national parks and historic sites would be given 48 hours to leave.