In Arkansas' Lower Delta, where the counties of Lee, Monroe and Phillips intersect, is an important part of the history of the United States. An interpretive boardwalk takes visitors into the heart of this headwater swamp and provides a view of the stone survey monument. Wayside exhibits tell the story of the Louisiana Purchase and describe the flora and fauna found in this ecosystem.

The Louisiana Purchase Historic State Park and Natural Area near Brinkley conserves a rare headwater swamp and a granite monument standing in the swamp’s interior. The monument marks the “initial point” established during an original survey of lands added to the United States as a result of the Louisiana Purchase. The area also protects a portion of the largest remaining headwater swamp in the Lower Mississippi River Valley. The swamp surrounding the marker is about six miles long and less than a mile wide and comprises the headwaters of Little Cypress Creek, making it a "headwater swamp.” The monument was listed on the National Register of Historic Places on February 23, 1972, and on April 19, 1993, the National Park Service designated the point a National Historic Landmark.

The Louisiana Purchase of 1803 more than doubled the size of the United States and brought all the territory that would become Arkansas under U.S. ownership. In 1815, President James Madison ordered a survey to establish a system for distributing land to veterans of the War of 1812.

On November 10, 1815, a party led by Prospect K. Robbins surveying a north-south line to be known as the fifth principal meridian crossed an east-west baseline that had been surveyed by a party led by Joseph C. Brown. The crossing of those lines became the “initial point” from which subsequent surveys of Louisiana Purchase lands originated.

Robbins’s party marked two trees about eighteen inches in diameter as witness trees to delineate the crossing.

While re-surveying the boundary between Lee and Phillips counties in 1921, surveyors Tom Jacks and Eldridge P. Douglas of Helena (Phillips County) discovered the witness trees. The L’Anguille Chapter of the National Society of the Daughters of the American Revolution in Marianna (Lee County) placed a monument on the site, dedicating it in ceremonies held on October 27,1926.

The Arkansas legislature authorized a state park on the site by Act 174 of 1961. Initial park development was accomplished with the aid of local citizens groups through the Green Thumb Program. In April 1977, the Arkansas Natural Heritage Commission added the swamp to the state Registry of Natural Areas and supplied funds for purchasing the park site.

Arkansas Tourism granted the commission a conservation easement on the site, thus providing additional legal protection for its natural and historical features. A 950-foot boardwalk was constructed from the swamp’s edge to the monument; in June 1981, it was designated a National Recreation Trail by the U.S. Interior Department. Informational panels about the Louisiana Purchase, the survey and the swamp were placed along its path.

The park’s botany includes species normally associated with swamps, such as swamp tupelo, bald cypress, black willow, and buttonbush, in proximity with upland species such as sweet gum, mulberry, Nuttall oak and sassafras. Many bird species can be observed in the surrounding swamp area.

Louisiana Purchase State Park and Natural Area is open daily from 6 a.m. until 9 p.m.