There are up to 10,000 puppy mills across the U.S.
That's more than enough to keep an animal lover awake at night.
Have you heard about these places? They're overcrowded and operate largely under the radar. Careless breeding practices means generations of dogs with health defects are born into unsanitary conditions, and female dogs are overbred and often killed once they are no longer of use, according to the ASPCA.