Located in the far north portion of the state, its municipal seat is the city of Angamacutiro de la Unión.

The name Angamacutiro originates from the Uapeani, Pauacume, and Tariácuri native indigenous languages,[citation needed] where it denotes "place on the edge of the canyon" or "lugar al borde de la barranca".

In the 16th century, the Spanish conqueror Nuño de Guzmán, when marching at the head of an expedition that was heading towards Nueva Galicia passed through this town, taking possession of it improperly, which caused a dispute, since the commander of Huango (Villa Morelos) claimed Angamacutiro as a parcel.

In 1866 there was a confrontation between the imperial forces commanded by Gen. Ramón Méndez and the Republican group known as los chinacos, the latter caused strong setbacks to the forces representing the intervention; in recognition of loyalty to the republic, the State Congress granted it on June 28, 1869, the name of "Villa Unión" is currently known as Angamacutiro de la Unión to its municipal seat.

It is bordered by the municipalities of José Sixto Verduzco to the northeast, Puruándiro to the east, Panindícuaro to the south, Penjamillo to the west and Pénjamo (Guanajuato) to the north.

[6] Native species include plants such as nopal, huizache and shrubs, and animals such as weasels, rabbits, squirrels, skunks, badgers, turtledoves and ducks.