The creation of the department of Tarn-et-Garonne in 1808, with parts of neighbouring departments, created a rich mosaic.

Mouillac, which was detached from the Lot department at the time, has retained its Caussenard characteristics in its customs and natural environment, with a hint of austerity. This appearance has been enriched by a generous rural heritage that needs to be restored, safeguarded and promoted. This heritage, characterised by its authentic and endearing architecture, has often been built at great sacrifice.

It is the essential legacy of small communities with virtually no other economic resources. Mouillac, a community of 550 hectares, has not escaped the exodus to towns such as Castelsarrasin, Moissac, Montauban and Caussade.

Today the population is growing again:
1904: 292 inhabitants - 1962: 59 inhabitants - 1975: 39 inhabitants - 1999: 67 inhabitants
2011: 87 inhabitants
The population is spread over six scattered hamlets, all with small buildings full of character.