Portsmouth is a city in the U.S. state of Ohio and the county seat of Scioto County. The municipality is located on the northern banks of the Ohio River and east of the Scioto River in Southern Ohio. The population was 20,226 at the 2010 census. Portsmouth's roots began in the 1790s when the small town of Alexandria was founded just west of where Portsmouth is today. Alexandria was flooded numerous times by the Ohio River and the Scioto River. In 1803, Henry Massie spotted a place to move the town away from the flood plains. He began to plot the new city by distributing the land and mapping the streets. Portsmouth was founded in 1803 and was established as a city in 1815. Alexandria soon disappeared. Portsmouth quickly grew around an industrial base with the completion of the Ohio and Erie Canal, and the construction of the N&W railyards and the B&O junction. This greatly benefited Boneyfiddle (which is a west-end neighborhood in Portsmouth), where grand buildings were constructed with the wealth from the commerce. As time passed, much of the commerce began to move towards Chillicothe Street, which is still today the main thoroughfare of Portsmouth. While Boneyfiddle is receiving new life, it is a shadow of its former self. Another notable part of Portsmouth's history in the 19th century was its importance on the Underground Railroad. It was located on a route that continued north to Detroit and into Canada.