Water is heated to a boil , creating steam that 's controlled under pressure . Once a popular form of transportation , few people use the river today . Kentucky 's City of Louisville and Maine 's Katahdin celebrated big birthdays this year . There are newer steamboats , including the American Empress and Miss Belterra .
Once a popular form of transportation , few people use the river today . Kentucky 's City of Louisville and Maine 's Katahdin celebrated big birthdays this year . There are newer steamboats , including the American Empress and Miss Belterra .