A breed of mastiff originally used to guard 'rock houses'--the places of business of drug dealers. Because of this, they were known as rock dogs until they were registered with the DRA in 1996. They have a strong instinct to protect everything, and can be aggresive towards strangers, but are good pets, and are safe for children to be around.
American mastiffs are smaller than most other mastiffs. They are light, hyper dogs, and are prone to chewing on things. They are not suggested as a owners' first dog, as they are harder than usual to train.

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