Pennsylvania played a central role in the passage 42 years ago of the federal Laboratory Animal Welfare Act - which for the first time set standards of care for lab animals. Today, known as the Animal Welfare Act, its standards are applied in the care all captive animals, including dogs in wholesale breeding kennels.

It was the plight of a Pennsylvania dog named Pepper - stolen in 1965 from a Slatington farm by animal rustlers who sold pets to medical laboratories - which galvanized the movement that led to the passage of the act and the birth of the modern animal rights movement.

Pennsylvania was home to many of the major animal rustlers, the notorious "dog swaps' and the infamous "Green Dragon" dog auction in Lancaster, where stray dogs and cats in chicken crates were sold alongside Amish crafts and baked goods. In Washington, one of the most tireless fighters for animal welfare was Pennsylvania Sen. Joe Clark.

In 1984, outrage over a film showing researchers at the University of Pennsylvania head injury clinic joking around as they performed violent whiplash experiments on helmeted baboons, that helped lead to passage of tougher federal protections.

This gripping story unfolds in a newly-published series by a Dan Engber, an editor at Slate and former vivisectionist . The Humane Society of the United States president Wayne Pacelle disagrees with Engber's conclusion that the "moral debate" has been settled. He also said facility non-compliance and failure to enforce the Animal Welfare Act remain a major issue. Read his blog here.