Ten years ago I was in San Francisco and dropped by the local SPCA's pet-adoption facility in the Mission District to make a donation. When I was living in the city years before, I had adopted a cat there that was still living with me, and I wanted to express my appreciation.
I discovered that in the intervening years there had been a change in the organization's policy. In the early 80s, the SPCA kept its abandoned pets for a certain period. If no one adopted an animal after that time, it would be put down. By the mid-90s, no healthy animals were being destroyed. Any dog or cat given to the SPCA in San Francisco would be cared for at the facility either until adopted or until the animal died from old age or disease.
This policy is a rare instance of a public organization fulfilling its mandate to the letter: the SPCA is, after all, a Society for the Prevention of Cruelty to Animals. When their policy included destroying dogs and cats it was more or less a surrender to economic reality, but it was obviously not something they carried out with a clear conscience.