This historical marker commemorates the fact that the 100th Meridian line, the invisible longitude line that runs from the North Pole to the South Pole, passes through Dodge City around one mile to the east. The line played an important in the history of the West and symbolizes the where the eastern part of the country ends and where the West begins. The marker is located near to the Wyatt Earp statue.
When the U.S. bought the Louisiana Purchase from France in 1803, the land on which Dodge City would be founded was part of the territory. The southern and western boundaries of the newly acquired territory were not clearly established, however. The issue was not settled until 1819 when Spain and the U.S. signed the Adams-Onis Treaty (1819). They agreed that one corner of the boundary was where the 100th meridian intersected with the Arkansas River, which is located 1.5 miles to the south of the marker. Later, the 100th Meridian was the western boundary of the Osage Indian Reservation. The 100th Meridian also roughly denotes where the boundary is between the dry western half of the country with the wetter, eastern half.