Two new riverboats in are due to be introduced by American Cruise Lines in 2022.
The new-builds will be the fifth and sixth in a new series of vessels first introduced in 2018.
Both new modern riverboats are yet to be named and will follow the debuts of American Jazz and American Melody on the Mississippi River this year.
The riverboats will be sister ships to 175-passenger American Melody, being launched on the Mississippi in August, including a walking track cantilevered above the fourth deck.
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The rapid expansion of the US domestic cruise market is being led by the company which has more than doubled in size since 2017.
The addition of the pair of new ships will see the fleet grow to 15 strong – five small cruise ships, four classic paddle-wheelers, and six modern riverboats.
American Cruise Lines also plans to continue building new small ships for US coastal itineraries.
President and chief executive Charles Robertson said: “American’s two new builds are welcome news for the industry here at home.
“They closely follow the two riverboats we are introducing this year and demonstrate our ongoing commitment to growth and leading the US small ship market.
“While the pace of our new builds is increasing, we are committed to maintaining the small capacity of our ships, which continue to accommodate just 100-190 passengers.
“This distinction across our fleet truly enables us to deliver the personalised and sophisticated experience our guests have come to expect.”