With its narrow, winding roads dotted with horse-drawn buggies and signs for homemade quilts, candles, jams and jellies, Pennsylvania's Amish country in Lancaster County attracts millions of tourists each year. But giant billboards along a main highway call attention to a less appealing local industry. "WELCOME TO LANCASTER ... HOME TO 100'S OF PUPPY MILLS," reads one sign. It was paid for by Last Chance for Animals, a national animal-advocacy organization that opposes commercial breeding facilities where hundreds of puppies are raised in cramped metal cages without proper food, veterinary care and often even fresh air.
Activists estimate that 200,000 puppies...