Benny, a shy dog at the Carson Animal Care Center in Gardena, Calif., waited weeks for his forever family. In December 2015, they finally came for him, and his unbridled joy at having a family to love was caught on video.

The Carson Animal Care Center is just one of more than 13,600 independent community animal shelters in the United States. Many use the generic terms SPCA or humane society in their names, but have no affiliation with the national organizations the American Society for the Prevention of Cruelty to Animals or the Humane Society of the United States. 

The ASPCA estimates that 3.9 million dogs enter animal shelters each year -- two-thirds arrive as strays and one-third are relinquished by their owners. Owners most commonly relinquish or give away their dogs because their place of residence does not allow pets; secondary reasons include behavior issues, divorce or death in the family, or simply not having enough time for the animal.

About 31 percent of the dogs brought into shelters each year are euthanized. Fortunately, more are adopted -- about 35 percent of shelter dogs, like Benny, are lucky enough to be adopted into a loving home by their forever family.