During the XIXème century, the city shakes the torpor accumulated to the previous century and, because prefecture, it had to progress and didn't want to remain a gloomy small city.
The remarkable administrator, the Baron d'Haussez was there, as well as mayor Soubiran, the first being interested stupendously in general in the flight of the Moors, the second trying to improve, to reform, to develop the county seat: widening of the streets, construction of the covered market and the theater, the city hall (present municipal library), the high school (1863), the church of St.-Jean-d'Août, etc.
Besides, it is in 1866 that the townships of Saint-Médard, of which the church, the oldest of the city, deserves the visit, Nonères and St.-Jean-d'Août were connected to Mont de Marsan.
This fusion and the administrative activity allowed the population to pass 4 514 inhabitants in 1804 to 9 300 in 1874.
