From CNNCNN) -- The great paddlewheel turned the Ohio River water to a froth as the Delta Queen steamboat, a floating National Historic Landmark, departed Cincinnati, Ohio, on its final scheduled voyage this week.
The ship carries Mark Twain's bell, took on Pearl Harbor survivors and has given passengers vacations since 1927.
2 of 2 more photos » The boat is a throwback to the 1800s and the era of Mark Twain, when thousands of steam-driven paddlewheelers plied the Mississippi River system.
The Delta Queen is the last of those operating as overnight passenger boats on U.S. waterways, giving riders a 19th-century experience on cruises complete with the carnival-like sounds of the steam-whistle calliope.
But it will dock permanently if Congress doesn't grant a safety exemption.
It left Cincinnati on Tuesday on a 10-day cruise down the Ohio and Mississippi rivers to Memphis, Tennessee, where it will unload what could be its final passengers.
"There are so few really authentic things left. Everything is a re-creation or a tied up old dusty museum," said Vicki Webster, leader of the grassroots Save the Delta Queen Campaign. "The Delta Queen is a breathing part of history and we have to keep as many of those as we can."
The frequent riders and steamboat aficionados are being punished, Webster insists.
Sherrin Kraus, 66, admires the Delta Queen as it passes by her home in Hanover, Indiana, each year.
"I've been in love with this boat since I was 5 years old," Kraus told CNN affiliate WLWT-TV when the ship arrived in Cincinnati. iReport.com: Share your photos, videos and memories of the Delta Queen
Kraus and her husband Ken boarded the Delta Queen's possible final voyage to celebrate their 45th anniversary. They told WLWT they decided to celebrate the occasion early out of concern the ship would not get another exemption.
"This was our 45th anniversary trip because we don't know what the future's going to bring, but we're worried," Kraus said. "If she doesn't survive this last onslaught, it's the end of an era."
The Delta Queen will go out of service if Congress does not grant the ship another exemption from a 1960s federal law, the Safety at Seas Act, which bans boats made largely out of wood because of fire hazards.
The current exemption, which expires at the end of October, has been given to the ship nine times over 40 years. See the Delta Queen's life in photos »
Supporters of the boat, which has roamed the nation's waterways since 1927 and helped the Navy ferry survivors of the attack on Pearl Harbor to San Francisco hospitals in 1941, are hopeful the ship will not play its famed calliope for the last time. iReport.com: Watch the ship depart as a calliope concert plays
The grassroots campaign is gaining traction and the support of high ranking politicians. House Minority Leader John Boehner, R-Ohio, said in a statement he would work with Rep. Steve Chabot, R-Ohio, to try to get an exemption granted if the House returns for a lame duck session to address economic issues following the election.
Supporters, including several mayors, agree with Webster that granting an exemption to the Delta Queen would be a way to help stimulate the economy without it costing taxpayers a dime.
Lee Powell, director of the Mississippi Delta Grassroots Caucus said the boat provides economic opportunities.
By docking and unloading nearly 200 passengers up to a dozen times a year, the Delta Queen helps to pump money into small cities along the heartland's rivers that are not normally tourist destinations.
Helena, Arkansas, which Mark Twain wrote in Life on the Mississippi "occupies one of the prettiest situations on the river," could suffer if the boat ceases operation.
"There are places in Helena that are essentially at virtually the levels of a third world country," Powell said. "They were impoverished before and now with the economic suffering, to choke off one of the good things they have is ridiculous."
The fight ahead is not uncharted territory for the Delta Queen, which fought down to the wire in 1970 to be given the exemption.
Rep. James Oberstar, a Minnesota Democrat who heads up the House Transportation and Infrastructure Committee, has refused to support the exemption, claiming the boat, with a steel hull but largely wooden superstructure, is a fire hazard.
Webster, who says she is "seething with anger" about the complaint, said the ship is outfitted with state-of-the-art fire safety equipment and a full fire crew on board.
"The heat detectors are so sensitive in the rooms if you take a shower and forget to close your bathroom door, the heat detectors go off," Webster said. "It's ridiculous. You literally could not have a fire on the boat because it would be put out in seconds."
Webster says the fight with Oberstar amounts to a labor dispute and that Oberstar is bowing to the Seafarers International Union which represented the boat's employees before it was bought by Majestic America Line. Oberstar and the union have both denied those accusations, but Webster insists simple politics are getting in the way of saving a national treasure.
"They're holding her hostage," Webster said. "That's like punishing a child because his parents are bickering or tearing down the Statute of Liberty because of a dispute between the owners of the land and the snack shop."
