Following the creation of the Royal Society for the Prevention of Cruelty to Animals (RSPCA) in the United Kingdom in 1824 (given Royal status in 1840), Henry Bergh founded the American Society for the Prevention of Cruelty to Animals on April 10, 1866 in New York City on the belief that animals are entitled to kind and respectful treatment at the hands of humans, and must be protected under the law. It is the oldest animal welfare organization in the United States. Founded in 1866, the ASPCA was the first humane organization in the Western Hemisphere. Buffalo's chapter, founded in 1867, is the second oldest.
ASPCA was founded to stop the injustices animals face across the United States. On February 8, 1866, Bergh pleaded on behalf of animals at a meeting at Clinton Hall in New York City. Some of the issues he discussed were cockfighting and the horrors of slaughterhouses. After getting signatures for his "Declaration of the Rights of Animals," Bergh was given an official charter to incorporate ASPCA on April 10, 1866.
On April 19, 1866, the first anti-cruelty law was passed since the founding of ASPCA, and the organization was granted the right to enforce anti-cruelty laws. At that time, there were three staff members at the ASPCA. In 1867, ASPCA operated its first ambulance for injured horses and advocated alternatives for inhumane actions toward animals such as horses, live pigeons, cats and dogs. By the time of Bergh's death in 1888, 37 out of the 38 states in the union had enacted anti-cruelty laws that were enforced by the ASPCA. Early goals of ASPCA focused on efforts for horses and livestock, since at the time they were used for a number of activities.
According to wikipedia