Here's a link to the article.
A couple of key excerpts:
"Long before there was even a dream of a United States of America, William Penn established the colony of Pennsylvania as a Holy Experiment. The city of Philadelphia was envisioned as a haven for immigrants fleeing religious persecution in their homelands."
"The physical evidence of William Penn’s vision remains strikingly present on the streets of Old City and Society Hill. There, within a half mile radius, we will find a variety of houses of worship that trace their origins to colonial times.... Each of these centuries-old congregations has a fascinating story in its own right. Even more remarkable, though, is the panoply of houses of worship seen as a whole. In America we take for granted that Presbyterians, Catholics, Quakers, and Jews all worship in the same neighborhood, their sanctuaries within striking distance of one another. But in the 17th century, the juxtaposition of denominations and faiths in the houses of worship on the streets of Philadelphia was radical, even jarring. Pennsylvania represented a conscious paradigm shift from the separatist impulse that spawned most of the other 13 British colonies in North America."