Nuevo León

The town is named after its patron saint, Charles Borromeo, and "Vallecillo" refers to its geographical location—a small valley at the foot of a hill. It is also believed that the name "Vallecillo" was taken from a place in Spain.

The northern part of the state of Nuevo León, located at 26°40′ north latitude and 99°58′ west longitude, at an elevation of 274 meters above sea level. It borders Lampazos de Naranjo and Anáhuac to the north; Sabinas Hidalgo and Agualeguas to the south; the municipality of Parás to the east; and Lampazos and Sabinas Hidalgo to the west.