Answer:
The border between Pennsylvania and Maryland was significant because it marked the southern border beyond which Quakers were not permitted to settle. This was due to religious tensions between Quakers, who were a minority in the region, and the dominant Anglican Church, which saw them as a threat to their own influence. The border helped to ensure that Quakers would not be able to spread their beliefs too far south, and helped to maintain the status quo of religious power in the region.