The Saint Helena principal meridian shares its initial point with the Washington Meridian at 31°N latitude and 91°09’15”W longitude. Though the Washington Meridian was surveyed in 1803, the Saint Helena Meridian was not officially surveyed until 1819. The Saint Helena Meridian, mainly located in Feliciana Parish, runs south of its Initial Point, passing one mile east of Baton Rouge, and extending to the Mississippi River. It controls all PLSS surveys in the Greensburg and southeastern districts of Louisiana, east of the Mississippi River. Westward ranges were run from the meridian to the Mississippi River, and eastward ranges were run to the western border of the territory controlled by the Saint Stephen's meridian. Survey townships were run south of the Louisiana base line to the Gulf of Mexico.
