The Northwest Lancaster County River Trail follows the route of the historic Pennsylvania Main Line Canal, tracing the Susquehanna River northwest from Columbia to Falmouth. The entire trail is paved. It passes through abandoned canals that were used during the Little Pittsburgh time. On the trail you can see remnants of iron furnaces which used iron ore and water power to heat the iron making it into slag. This would pollute the water along with the land around the furnaces.