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The basics of map drawing

You can access a free district building software at:

Dave's Redistricting App 2020 (DRA 2020)


How to get started with Dave's Redistricting App

What data is used?

  • The state will use 2020 Census data to draw new maps once it becomes available in the spring of 2021.  DRA 2020 uses 2010 Census data along with election data from 2016.

  • It will not be possible to draw complete district plans using DRA until after the 2020 Census data is delivered to the state.

  • Yes, there will be quite a large difference in the district sizes from 2010 to 2020.  During the last legislative session, Fair Maps Texas supported legislation that would have slowed down the redistricting process and created a timeline.  

  • It also is problematic that the Legislature is currently holding public input hearings around the state, collecting input from the public on where their communities of interest are located.  While they have do have population estimates from state demographers, they are essentially flying blind until the official 2020 Census data is delivered from the federal government.

How many districts should I draw, and what is their projected population size?

  • 39 U.S. Congressional districts with an average size of ~750,000 people

  • 150 State House districts with an average size of ~195,000-197,000 people

  • 31 State Senate districts with an average size of ~947,000 people

All districts must be contiguous.

Majority-Minority and Opportunity Districts -Majority-Minority districts: There is not an explicitly required number of districts that Pennsylvania needs in which the majority of its population is comprised of people of color. However, the Voting Rights Act of 1965 protects minority groups from having the power of their vote diluted, so that they can have regular and meaningful opportunities to elect a candidate of their choice. DistrictBuilder defines a majority-minority district as one in which people who are nonwhite ethnicities are in the majority. In Pennsylvania, this generally works out to two districts in the Philadelphia area.

Compactness Score

Population Equivalence

County Splits

Precinct Splits

Public Input - link to testimony index (hopefully) by region

Demographic shifts leading into 2020 - reports from demographer

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