, located at the southeast corner of
Temple Square in
Salt Lake City. A principal meridian and base line are usually established based on a preselected initial point, often some distinct geographical feature. As an example, the first established initial point in California was the
Mount Diablo meridian. It was chosen because the summit of
Mount Diablo could be seen for many miles around and could be referenced for surveys. In other cases, a meridian and a base line were chosen separately based on other geographical features. For example, the
Fifth principal meridian in the new
Louisiana Purchase was established in 1815, with its southern end based on the
confluence of the
Arkansas and
Mississippi Rivers, and extended northward from that point. The eastern end of the base line was chosen as the confluence of the
St. Francis and Mississippi Rivers and extended westward. The initial point would be established where the meridian and the base line crossed, which turned out to be in the middle of a swamp in eastern
Arkansas. This point is now located in the
Louisiana Purchase State Park. Some initial points were chosen based on existing markers. The initial point for the
Gila and Salt River meridian was established based on an existing marker that had been set up in 1851 to mark a point on the
Mexico–United States border before the
Gadsden Purchase. Many of the initial points in the United States have been listed on the
National Register of Historic Places. Notable initial points include: •
Beginning Point of the U.S. Public Land Survey •
Initial Point (Oklahoma) •
Initial Point of Boundary Between U.S. and Mexico, California •
Initial Point of the Gila and Salt River Base Line and Meridian, Arizona •
Mason and Dixon Survey Terminal Point, West Virginia ==See also==