Beginning as early as the 1890's and continuing into the 1950's, a fleet of battered steamboats and barges known as the Hard Coal Navy dredged coal from the Susquehanna between Danville and Sunbury and on the North Branch. Their industrious captains hauled up coal from the river bottom, waste that had washed down from the anthracite coal fields of the Wyoming Valley. This was a seasonal industry, and at its height as many as 200 barges worked the river from Nanticoke to Harrisburg. The recovered coal was sold to utilities, industries, and schools, and in 1919 and 1920 more than 2,000,000 tons of river coal were harvested each year.