The Jefferson National Expansion Memorial is a park located in St. Louis, Missouri, near the starting point of the Lewis and Clark Expedition. It was designated as a National Memorial by Executive Order 7523, on December 21, 1935, and is maintained by the National Park Service .
The park was established to commemorate:
* The Louisiana Purchase, and the subsequent westward movement of American explorers and pioneers;
* The first civil government west of the Mississippi River; and
* The debate over slavery raised by the Dred Scott case.
The memorial consists of a 91acre park along the Mississippi River on the site of the earliest buildings of St. Louis; the Old Courthouse, a former state and federal courthouse that saw the origins of the Dred Scott case; the 45000sqft Museum of Westward Expansion; and most notably the Gateway Arch, a steel catenary arch that has become the definitive icon of the city.