Fifth principal meridian

The Fifth principal meridian, often denoted the "5th Meridian" or "PM 05," is a principal meridian survey line used in the United States for land claims in the Public Land Survey System . It was first surveyed in 1815. The meridian, a north-south line, starts from the old mouth of the Arkansas River and runs north. Another survey line related to it is the base line running west from the old mouth of the St. Francis River. These survey lines govern all land surveys in four states and a large portion of the land surveys for two more. Monuments have been erected where the two lines meet at 34°38′44″N 91°3′42″W, and the surveyors' skill has been commemorated at the Louisiana Purchase State Park in eastern Arkansas. The Fifth principal meridian is nearly coincident with 91° 3′ 42″ longitude west from the Greenwich meridian.

In Arkansas, Missouri, Iowa, and North Dakota, it is the sole principal meridian used in the PLSS. It is used in Minnesota west of the Mississippi River and west of the third guide meridian north of the river. In South Dakota the meridian covers roughly the eastern half of the state: all land east of the Missouri River plus the surveys on the west side of the river to a limiting line following the third guide meridian of the sixth principal meridian system, White River, and the west and north boundaries of the Lower Brule Indian Reservation.

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