In December 1808, Thomas Lincoln, father of Abraham Lincoln, purchased the 300-acre Sinking Spring Farm. A magnificent white oak tree stood at the western edge of the farm. The tree served as a boundary marker and survey point for determining the property lines. The metes and bounds system of the period allowed for the use of large trees, boulders, and even fence lines as boundary markers between properties and was a common practice and readily accepted throughout the 19th and 20th centuries.
The Boundary Oak was first identified as a specific boundary marker in the original 1805 survey of the farm. A landmark to countless early travelers, the Boundary Oak was located less than 150 yards from the cabin in which Abraham Lincoln was born February 12, 1809. It is estimated that the tree was 25 to 30 years old at the time of Lincoln's birth.
Time, weather, insects, and even disease took their toll on the mighty oak. Efforts were made, as early as the 1920s, to save the oak but all failed. Finally it was cut back to just a stump and eventually cut down completely in 1986. Before its death in 1976, the Boundary Oak grew to nearly six feet in diameter, 90 feet in height, and had a crown spread of 115 feet.
The Boundary Oak Tree was approximately 195 years old and until its death, the great white oak remained the "last living link" to Abraham Lincoln and was of considerable historic interest and value.