<P> Two different canal systems were constructed on the lower Susquehanna to bypass the rapids . The first was the Susquehanna Canal, also called the Conowingo Canal or the Port Deposit Canal, completed in 1802 by a Maryland company known as the Proprietors of the Susquehanna Canal . The second was the much longer and more successful Susquehanna and Tidewater Canal . The canals required additional dams to provide sufficient canal water and navigation pools . </P> <P> As the industrial age progressed, bridges replaced ferries, and railroads replaced canals . The railroads were often constructed on top of the canal right - of - way along the river . Many canal remnants can be seen in Havre de Grace, Maryland, along US Route 15 in Pennsylvania, and in upstate New York at various locations . These latter remnants are parts of the upstream divisions of the Pennsylvania Canal, of privately funded canals, and of canals in the New York system . </P> <P> Today 200 bridges cross the Susquehanna . The Rockville Bridge, which crosses the river from Harrisburg to Marysville, Pennsylvania, was the longest stone masonry arch bridge in the world when it was constructed, a distinction that it continues to hold . It was built by the Pennsylvania Railroad in 1902, replacing an earlier iron bridge . Two seasonal ferries continue to operate across the Susquehanna . The Millersburg Ferry at Millersburg, Pennsylvania is a practical ferry for up to four vehicles and 50 passengers, while the Pride of the Susquehanna, based at Harrisburg, provides a passenger - only pleasure cruise . </P> <P> Most of the canals have been filled in or are partially preserved as a part of historical parks . Dams generally are used to generate power or to provide lakes for recreation . </P>

Where is the susquehanna river on a map