Which organization was founded primarily to address issues of animal rights in the United States?

The Humane Society of the United States (HSUS) was founded in 1954 and focuses on various issues related to animal welfare, which includes championing the ethical treatment of animals. Its mission encompasses a broad spectrum of activities aimed at preventing animal cruelty, supporting animal rescue operations, advocating for stronger animal welfare laws, and promoting the humane treatment of all animals.

While the other organizations listed, such as the Animal Legal Defense Fund, People for the Ethical Treatment of Animals (PETA), and the Animal Welfare Institute, also address animal rights and welfare, HSUS has a larger recognition as a main advocate for these issues on a national level. HSUS engages in legislative advocacy, public education, and direct animal care, positioning itself as a leader in the movement to improve the care and treatment of animals across the United States.