Bernard Ratzer was a military surveyor who mapped the Gowanus marshes and farms in 1766. The map was calibrated to 2004 New York City digital base map data by Eymund Diegel, urban planner, using surviving common remnant street intersections (Red Hook Lane, Flatbush Ave). This 1766 map is the most accurate known survey of the Gowanus area, and is presented here with current buildings and draft historical research notes for finding out more about your neighborhood.
http://brooklynhistory.org/docs/Ratzer_map.pdf
