Both the Pennsylvania State Constitution and Philadelphia City Charter set limits on what districts may look like, but only in very general terms. The Constitution, in Article II, Section 16, calls for districts to be "compact and contiguous territory as nearly equal in population as practicable." The City Charter calls for each district to be made up of "a ward or contiguous wards containing as nearly as possible the population factor obtained by dividing the City's population at the preceding decennial census by ten."
The shape and nature of Congressional Districts are governed by a web of laws and court cases, the most important principle of which is known as "one person, one vote". That is, districts must be drawn as much as possible in such a way that no one person's vote carries more weight than one person's in any other district.
The only exception to this is the Constitutional requirement that each state must have at least one representative, which means that residents of some of the most sparsely populated states unavoidably have disproportionately large representation in Congress. This system can also work against sparsely populated states. There is currently a challenge to the fixed size of the House of Representatives pending in federal court, based on the grounds that it leads to dramatically unequal apportionment, violating the principle of equal representation.
Compiled by Committee of 70
Committee of Seventy + 
