Diana and David Carlson have traveled around the world over the years: Egypt, South Africa, China, Prague, Berlin and more.

“My husband’s getting to the point where he says, ‘I just don’t like those long plane trips,’" says Diana Carlson, 73. That’s fine with her. “I say, ‘Okay, we’ll go on the boat again.’ I’ll go on it as often as I can.”

By “the boat,” Carlson means the American Queen, a six-deck paddle-wheeler that plies the Mississippi River as the flagship of the American Queen Steamboat Company. For all the Southern California couple’s globe-trotting, they’ve sailed nearly 20 times with the cruise line that’s devoted to U.S. rivers.

The Carlsons are exactly the kind of customers the operators of American river cruise lines want to reach: They have the time and ability to travel, an interest in exploring U.S. sites and — importantly — they know that river cruising exists in the United States.

“I really believe the demand is there,” says Charles B. Robertson, president and CEO of American Cruise Lines, which operates a fleet of 12 small river and coastal ships that touch 30 states. “It’s a matter really of raising awareness about cruising as an option in this country. The demand for river cruises globally is enormous, and I think most people just aren’t aware yet that it’s actually an option here.”

Baby boomers are the group that operators are most keen on reaching. Robertson said his company has historically attracted cruisers 65 and older, but are attracting more in their 50s with amenities on new boats, like yoga rooms, gyms and unique gathering areas.

“People that cruise on our boats need two things: time and money,” says John Waggoner, chairman and CEO of American Queen Steamboat Company. “Because of that, boomers are ideal. Most of them have traveled all over the world. They want to stay closer to home, they want to learn more about the U.S.”

About 80 percent of the steamboat company’s passengers are baby boomers. Waggoner said depending on the boat in question, demographics on board skew toward 65 or 70, plus or minus 10 years. Cindy Anderson, an owner of the travel agency USA River Cruises, says the market has largely been travelers 65 and older.

European river cruising got a huge popularity boost in the past decade during the run of the TV period drama “Downton Abbey” — not because of any particular plot line, but because Viking River Cruises was a sponsor of the PBS Masterpiece series. U.S. audiences who couldn’t get enough of the Crawley family and their staff also got an eyeful of the company’s boats, cabins and destinations.

Although Americans have been traveling on U.S. rivers for centuries, the modern river-cruise industry in the country is still nascent and dominated by two companies. American Cruise Lines started sailing in 2000, while major operator American Queen Steamboat Company launched its first ship in 2012. Both have seen accelerated growth in recent years. Between them, they cover waterways including the Mississippi, Ohio, Tennessee, Cumberland, Hudson, Columbia and Snake rivers as well as coastal areas in New England, the Southeast and Alaska.

Itineraries are often focused on history or nature, with a heavy dose of Americana. Cruise lines organize themed trips around the Civil War, Kentucky Derby, music, food or bourbon. Trips tend to include alcohol, and most shore excursions and can cost far more than a typical Caribbean cruise, between $6,000 to $10,000 a week per couple, depending on the line.

“I think a lot of people have not really explored the United States in that way,” says Colleen McDaniel, editor in chief of the news and review site Cruise Critic. “And it’s a really fabulous way to do it. The pace is a little bit slower, which is great for some people."

The Cruise Lines international Association doesn’t break out statistics for river cruising in the United States, but the two biggest players say they are having to add ships to keep up with the demand.

American Cruise Lines can carry about 80,000 passengers this year, with that number expected to grow as more boats come online; two more new vessels will be added in 2021, bringing the total to 14. The line, which sails paddle-wheelers, coastal ships and modern riverboats that carry between 100 and 200 passengers, has more than doubled capacity since 2015.

American Queen Steamboat Company needs about 46,000 customers a year to fill the six vessels it owns under two brands — the namesake steamboat company and the recently acquired Victory Cruise Lines. The operator christens its latest addition American Countess, a 245-passenger steamboat built using the hull of a former casino boat, in April. Last year, the operator acquired Victory and its two coastal vessels, and is building a third.

“They want to get the ships on those rivers fast,” McDaniel says. “So I think that represents the demand that’s out there.”

Viking — now an industry powerhouse with 78 ocean and river vessels — is making bigger moves in the United States. The company recently announced a new expedition ship that will sail to United States and Canadian destinations on the Great Lakes.

The Associated Press reported last week that Viking also plans to start Mississippi River cruises in 2022; the operator has been talking about plans to enter the market for several years. More details were not immediately available.

U.S. law says lines that sail only domestic itineraries must meet stringent requirements that keeps foreign operators out. Vessels must be built in the United States, staffed by American crew, and inspected by the Coast Guard, among other rules. It wasn’t clear how Viking planned to meet those requirements, but competitors say they hope the line’s arrival will drum up more attention for the still-niche sector.

Anderson, whose travel agency focuses on American rivers, said current global events are also driving interest in local exploration.

“A lot of people are not leaving the United States because of this new virus,” she says, referring to the novel coronavirus that has sickened more than 81,000 people and killed more than 2,770. “We’ve had a huge amount of cancellations for overseas, but we’ve also had double the amount of bookings for the U.S. now.”

For 77-year-old Al Elliott of Georgetown, Tex., the rivers have been a great place to spend his retirement (and his kids’ inheritance, he joked). He takes Amtrak to all his cruises and counts a wine cruise as one high point.

“I think my liver’s still trying to dry out from that one,” he says, though he’s hardly done with the theme. “They have a beer cruise I want to go on.”

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