The phylloxera root louse was destroying the prestigious French winegrapes, and therefore, destroying the economy of France. France assigned the preeminent French scientist, Pierre Viala, the task of finding a cure for the phylloxera plague. This investigation brought him to the United States and to the home of Thomas Volney Munson in Denison, Texas. The two scientists collaborated on the problem for several days in Denison and various other locations in Texas to view the native grapes of Texas in their natural habitat: the soils of the Charante and Denison are very similar and therefore should have grape species capable of growing in either location. T.V. Munson suggested that the only way to save the French vineyards was to graft the Vitis vinifera varieties to resistent rootstocks. Munson knew that the Texas rootstocks were resistent to phylloxera and at his suggestion Viala agreed that it was a good plan of action.

Thousands of bundles of Texas rootstocks were shipped to France where Viala and other French scientists starting educating the French winegrowers about the enormous grafting tasks that lay ahead. The grafting literally continues to this day.

For his monumental contributions to France, T.V. Munson was awarded the highest award that could be given a foreign civilian, the Chevalier du Merite Agricule, and was inducted into the Legion of Honor in 1888. To commemorate the award 100 years later, a Centennial Celebration was held in both Cognac and Denison, where identical plaques were presented to each city and official delegations visited both countries.

While the Deniosn delegation was in Cognac, Mayor Francis Hardy asked David Munson of the W.B. Munson Foundation to investigate the possibility of establishing a formal relationship between the two cities. This was accomplished. In October 1992, a delegation from Denison went to Cognac and, in a formal ceremony, established the Sister City relationship.

In a reciprocal visit, an official trade delegation from Cognac visited Denison in 1993 to begin the economic development strategies between the two cities. Upon arrival of the Congnac delegation, Denison Major Ben Munson stated, "This Sister City relationship marks the beginning of an international economic development venture which will significantly benefit the peoples of Denison and Cognac for generations to come." Educational and professional exchange programs were implemented in 1994.

Economic development and trade are of paramount interest to both cities, and with a relationship that spans over 100 years, this new international venture should mature rapidly and reap great rewards to both cities.