Stroudwater is a small historic village in the city of Portland, Maine.
Source: The Miriam and Ira D. Wallach Division of Art, Prints and Photographs: Photography Collection, The New York Public Library. “Tidal Mill at Stroudwater, Maine.” The New York Public Library Digital Collections. 1860 – 1920. http://digitalcollections.nypl.org/items/510d47d9-ab22-a3d9-e040-e00a18064a99
* I believe the image above is incorrectly labeled, and is not the actual Tidal Mill at Stroudwater. The real “Tidal Mill at Stroudwater” bridged the Fore River in the village of Stroudwater as depicted in the postcard below.