Which congressional districts in Pennsylvania are the most populated?

Each of Pennsylvania's 18 congressional representatives in the 113th U.S. Congress represented districts with a population of slightly more than 705,000, based on 2010 Census data. Thirteen of the 18 districts had a population of 705,688 while the remaining five districts had populations of 705,687 each.

In the 1964 case Reynolds v. Sims, the United States Supreme Court ruled that apportionment of congressional districts shall be based on the principle of "one person, one vote." In practical terms this means that when states redraw congressional districts every 10 years following each U.S. Census, each congressional district receives a roughly equal share of the state's population.