According to the American Humane Society, the concept for Adopt a Shelter Dog Month was drummed up back in 1981 in an effort to help the estimated three million to four million unwanted dogs find loving homes. And as you can imagine, it's usually not the puppies who are at risk. Dogs over the age of 7 are usually the bulk of shelters' residents. And to make matters worse, nearly three million adoptable dogs and cats are put to sleep each year.