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In page Monongahela, Pennsylvania:

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Monongahela was founded in 1769 on a tract of land near the confluence of Pigeon Creek and the Monongahela River. It is the oldest settlement in the Monongahela River Valley and most likely the oldest in Washington County.[citation needed] The word Monongahela is Native American in origin, meaning "falling banks". The Monongahela tribe was also indigenous to the area prior to the settlement of the city.