Championing Spay/Neuter Helped Define ASPCA in the 20th Century and Beyond
Throughout 2026, the ASPCA is sharing highlights from our organization’s rich and sometimes unexpected 160-year history.
February is Spay/Neuter Awareness month, but did you know that these procedures weren’t widely used for American pets until the 1970s? This evolution came about in response to a dire, decades-long need: As the middle class expanded and pet ownership became increasingly mainstream throughout the 1900s, unplanned litters surged, creating a cat and dog overpopulation crisis.
By preventing unwanted litters, spaying and neutering can reduce shelter intake and create more space and opportunities for pets to be adopted. Recognizing the need for a humane, scalable solution, the ASPCA invested early in effective spay/neuter campaigns, expanded community access, and veterinary training programs to reduce the needless euthanasia of healthy animals. This work continues to grow today, with the ASPCA operating our own surgical centers and supporting spay/neuter efforts through education, shelter grant funding and legislative advocacy across the country.
Even so, understanding our history means acknowledging not only moments of progress but also the uncomfortable, even painful chapters that shaped our world as we know it today. Being honest about the past helps us recognize how far animal welfare has come — and better appreciate the advancements we continue to make.
In the 1870s, the destruction of unwanted animals was carried out in ways that were far from what we now consider humane. In New York City, as many as 700 homeless dogs and cats could be drowned in a single day. Animals were loaded, 50 at a time, into a large, wire crate that was lowered by crane into the East River. ASPCA founder Henry Bergh designed this system himself, believing it the “quickest and kindest way” to carry out this grim task.
In 1894, six years after Bergh’s death, the ASPCA agreed to take over New York City’s animal control services, which included “the humane destruction of captured animals at the city pound.” That year, 24,275 animals were put to death at the ASPCA’s shelter in Brooklyn. By the 1920s and 1930s, the ASPCA was running shelters in each of the city’s five boroughs and handling more than 300,000 animals annually. In 1928, at least 280,000 animals were killed (by this point, the ASPCA and many other shelters were using chloroform or gas chambers).
It wasn’t until the late-1960s/early-1970s that heightened awareness of this ongoing tragedy led to a societal shift of normalizing the surgical sterilization of pets. The estimated number of homeless dogs and cats dying across the country at the time was in the tens of millions.
In 1973, the ASPCA mandated that all cats and dogs adopted from our NYC shelters be sterilized, either by the ASPCA or a veterinarian of the adopter’s choice. Over the next two decades, as other cities and states adopted this policy, unplanned litters declined and fewer animals entered shelters.
In 1994, a century after assuming the animal control role in NYC, the ASPCA passed the torch to a new organization, Animal Care Centers of NYC. This allowed the ASPCA to pour resources into creating efficient, high-volume spay/neuter programs — in our hometown, and beyond. We introduced our first mobile surgical clinic in New York City in 1996, which eventually grew into a fleet. Ten years later, for the first time in NYC’s history, more animals were adopted from shelters than were euthanized.
Power in Numbers
Data can paint a powerful picture. Since 2002, the ASPCA has spayed and neutered more than 675,000 animals in New York City, mostly cats and dogs, at mobile units and stationary clinics.
Our reach extends to underserved communities in Los Angeles, where we have sterilized more than 164,000 animals — cats, dogs and 261 rabbits — since 2015 at our full-time stationary clinic in Los Angeles and mobile units. The ASPCA is opening a second stationary clinic in Carson, California, in 2026. At our Miami clinic, more than 20,000 animals have been altered since 2019.
The health benefits of spaying and neutering individual pets are widely touted by animal welfare organizations and veterinary experts, but the bigger impact is reflected in shelter data. The euthanasia rate for animals in U.S. shelters has continued to trend downward over time, especially for cats, who have been served by the growth of community cat programs providing targeted spay/neuter services for this population.
The impact of spaying and neutering is also evident in adoption statistics. In New York City, the adoption rate in 2025 was 88% for dogs, and between 91-99% for cats and small animals. Other cities have had similar successes. Adoption data for 2025 from Shelter Animals Count, a nationally recognized nonprofit that is now a program of the ASPCA, shows that private shelters and rescue groups placed 86-91% of dogs and 85-88% of cats, and government shelters and shelters with municipal contracts placed between 51-60% of their dogs and 55-73% of their cats. (Government organizations and shelters with municipal contracts have higher rates of other outcomes, such as pets returned to owners, so their adoption rates are typically lower than those of other types of shelters and rescues.) In addition, in 2025, 25% of dogs and 23% of cats who entered shelters were already spayed or neutered.
“Spaying or neutering is more than just a healthy choice for the individual pet — it’s a lifesaving one,” said Dr. Carolyn Brown, who has overseen the ASPCA’s spay/neuter operations in New York City since 2011. “Every surgery prevents the birth of puppies or kittens who may end up in a shelter, taxing their resources, capacity for care and ability to find homes for everyone. In animal welfare, few actions make a more powerful difference.”
A Monumental Acquisition
In 2015, the ASPCA advanced our efforts to curb pet overpopulation by acquiring the Asheville, North Carolina-based Humane Alliance (now the ASPCA Spay/Neuter Alliance), the nationally recognized pioneer in the development and dissemination of sophisticated, high-quality, high-volume spay/neuter techniques since 1994.
The ASPCA Spay/Neuter Alliance operates the nation’s foremost spay/neuter clinic and veterinary training programs, teaching best practices to hundreds of veterinary students and veterinarians annually. Its surgical volume directly correlates with lower euthanasia rates for cats and dogs in the region. Since 1994, more than 566,000 cats and dogs have been spayed or neutered at this facility; today, pet adoption rates in Asheville shelters exceed 90%.
Dr. Karla Brestle, a veterinarian who joined the ASPCA Spay/Neuter Alliance in 1998, helped establish a clinic mentorship program for other organizations delivering high-quality, high-volume spay/neuter services. Today, the ASPCA Spay/Neuter Alliance’s business model has enabled the opening of more than 200 high-quality, high-volume spay/neuter clinics nationwide, which have sterilized more than 13.6 million companion animals from 2005 to 2024.
“We showed how clinics could alter a specific quantity of animals per day with a specific number of staff to make a dent in their community’s animal population,” says Dr. Brestle. “We gave them the formula, and they ran with it.
We’re happy to announce that the ASPCA Spay/Neuter Alliance’s headquarters is expanding, thanks to funding from a longtime supporter. By December 2027, it is expected to perform more than 26,000 surgeries annually.
“We know spaying and neutering are the most effective ways to reduce pet overpopulation and euthanasia,” Dr. Brestle added. “We’re excited for more opportunities to focus on what we do well.”
Related story in this ASPCA 160 series:
Share this page: