Jon Skinner, a forester with the Missouri Department of Conservation, presented the city with a plaque this week announcing the honor.
The tree has been under observation by the state for a number of years. Will Branch, an arborist with the University of Missouri and a Monett native, is credited with discovering the tree.
Branch and two colleagues, Ryan Russell and Austin Lampe, were fishing at Roaring River State Park one day and decided to explore Monett's South Park. They found the tree, which has since been measured and tallied in the state's evaluation process.
According to Skinner, trees are assessed by the circumference of their trunk, their height and the spread of the branches for a crown. The Monett sassafras is 186 inches around, and 54 feet high and spreads to a crown of 36 feet in two directions. Placed into the state's formula, the tree had the most points of any sassafras.
The tree is of unknown age. Skinner called it "ancient." He cautioned that the tree is most likely hollow and may be at risk of falling. Because of its location on the southeast slope of the old park, behind the exercise yard and the golf course, the tree is not a hazard.
Park Superintendent Russ Balmas said the plaque will probably be placed at City Hall. He planned to put up signs directing visitors to the tree for viewing.