Everyone is welcome to share and repost any of these map links. There is no need to ask first. Please follow these simple rules:
1. When you post a map link, please encourage your readers to click the "Map Tips" link in the upper left corner. Many questions about the maps will be answered by those tips.
2. It is preferred that you use a map link instead of embedding a 'live' map.
3. Include in your post a credit thanking https://mappingsupport.com.
4. Do not use these map links for any commercial purpose.
Be patient. If you zoom in a lot on a map (zoom level 13 or higher) then the congressional district lines are 2-tone yellow and red. This coloring makes the district lines extremely easy to see on any of the various basemaps. The data to produce those lines comes directly from federal GIS (Geographical Information System) server(s). Sometimes it may take a few seconds for data to appear on the map. It all depends on how much other work the server(s) are trying to do at the same time.
The map is displayed by Gmap4 which is an enhanced Google map viewer. The ability to turn on an overlay that shows the congressional district boundaries is now a permanent built-in feature of Gmap4. Additional related features have been added.
The congressional district boundaries are current as of January 2017 and correctly show the districts for the 115th congress.
Action Item: Use this map to show your representative examples of grossly shaped congressional districts. If your representative is not already a co-sponsor of H.R. 3057, then ask them to either (1) become a co-sponsor or (2) explain to you exactly why they are in favor of gerrymandered congressional districts.
In addition to these congressional district maps, similar maps have been prepared for all state legislature districts for all states. The corresponding "Tips" page for the state legislature district maps is at https://goo.gl/82UT5H.
Questions, corrections, comments, etc can be emailed via this contact page or posted on the Gmap4 Facebook page.
The term "gerrymander" refers to drawing district boundaries in order to favor a certain political outcome. For more information on gerrymandering and how elections to the U.S. House of Representatives might have a different outcome without this unlawful practice, just do a google search on: congressional district map gerrymander.
Want to know who decides where voting district boundaries are drawn in your state? The Brennan Center for Justice (New York University School of Law) has complied that information here. This analysis covers both congressional districts and state legislature districts.
The Brennan Center also posts periodic updates on the status of the various lawsuits underway in several states challenging gerrymandered voting districts. Here is their late April 2017 update.
Another excellent source of information on the status of lawsuits that challenge gerrymandered voting districts is this Election Law Blog.
Log of Map Changes
August 9, 2017
Changed the congressional maps so they have the same look-and-feel as the state legislature maps. When a congressional district map opens the district colors are now semi-transparent instead of solid. And when you click a congressional district the popup now displays the elected person's social media links.
Also added the section "3 Data Resolutions" to this page of map tips.
Due to a fundamental change in how congressional district lines are displayed, the map no longer supports displaying both congressional district lines and state legislature district lines.
March 4, 2017
Added the button "Bizzare Districts". There are map links with examples from 21 states.
February 24, 2017
The congressional district boundaries are now a permanent 'built-in' overlay.
The '&congress=' link parameter has been added. See the section 'Create Custom Map Link' above for details.
January 31, 2017
Changed the name of the link in the upper left corner of the map from "About this map" to "Map Tips".
Added the button "Create Map For One District" to the Tips page.
Rearranged the buttons on the Tips page
January 29, 2017
Initial map launched.
My name is Joseph Elfelt and I produced the congressional district map you are reading about. To be honest, I feel the work I am doing to help shed light on gerrymandering is sufficiently important that I intend to continue producing similar maps even without any financial support. But just like you, the reality is that I need to buy groceries, pay for housing and keep up with life's other bills.
To the best of my knowledge, the congressional district map I produced is the first one that lets anyone make their own custom map link that highlights any district when the map opens.
I have also produced maps that show all of the state legislature districts. To see these maps, click the basemap button on any map - it is next to the "Menu" button. Then look under the "Overlay" heading (mobile users scroll down) and click "State_legislature_districts". These state maps have their own Map Tips page.
If you would like to support my work you can do so through PayPal. You do not need a PayPal account to donate. All you need is a credit card.
Open the Google + GIS Congressional District Map
Basic Map Tips
The map will only open if your browser is online.
If you open the map on a desktop or laptop computer then you will see a mouse-oriented interface. If you open the map on a mobile device then you will automatically see a touch interface.
The semi-transparent colors look the best when the basemap is the google street map. If that is not the current basemap then you can click the basemap button (next to the "Menu" button) and select "Street Map Google".
If you click a district then you will see a display showing the name of the congressperson and names of the senators for that district along with their party affiliation, homepage and social media links. Also the district will be highlighted with a color showing the party affiliation of the congressperson.
To change the basemap, click the basemap button (next to the Menu button).
To search on an address, coordinates or a placename, click Menu ==> Search. A search bar will appear at the top of the screen. After the map re-centers at the thing you searched for, then click the map and the popup will show data for that congressional district.
To turn on geolocation, click Menu ==> My location. The geolocation symbol will follow you as you move. If you use this feature then you should zoom in the map so the district lines are 2-tone yellow and red. This shows the congressional district lines with the highest resolution data that is available from the U.S. Census Bureau.
The map has several built-in overlay layers that can be turned on/off. One of those built-in layers will show the congressional district boundaries and another layer will show state legislature district boundaries. To see the list of overlays click the basemap button and then look under the "Overlay" heading. Mobile users will need to scroll down.
An overlay layer with a number in front of it is 'on'. Click a layer name to turn it on/off. The highest numbered layer is "on top". Usually the "top" layer can be clicked and a popup will appear showing information about the thing that you clicked.
3 Data Resolutions
Low resolution lines
A map that shows congressional districts for all of the USA is displaying low resolution district lines. If you try to zoom in too far then you will see a message inviting you to select a state so you can see district lines with better resolution.
Medium resolution lines
When a map shows all the congressional districts for one state with semi-transparent colored fill then you are seeing medium resolution district lines.
When you are looking at medium resolution data and click a district the map will automatically center and zoom such that all of the district is displayed on your screen.
High resolution lines
If you keep zooming in then at zoom level 13 and higher the district lines will be two-tone yellow and red. There will not be any semi-transparent fill (unless you click a district). You are now seeing high resolution district lines.
When you are looking at high resolution data and click a district the map center and zoom will remain the same.
Here is an example centered on New York city and showing medium resolution district lines. Look at the center of the map and the district line just under the name Brooklyn. Then zoom in one step and notice the difference when the high resolution lines are displayed.
Bizarre District Examples
Each map link below will show the congressional districts for one state and have one of those districts highlighted. The example from Michigan has a particularly bizarre shape. The fact that there are examples from 21 states shows that gerrymandering is a widespread problem.
While some of these highlighted district seats are held by democrats, most of these seats are held by republicans.
New Jersey 12th
South Carolina 2nd
West Virginia 2nd
Create Custom Map Link
Here are examples showing how anyone can make a custom map link that will display the congressional district boundary data in a certain way when the map opens. These examples will automatically pick a center for the map and zoom level based on the data that is being displayed.
Note the word "all" in these first three examples. These maps display all the congressional district boundaries for all the states. This is low resolution data and there is a limit on how far in you can zoom.
Display all the states and all the district boundaries:
Display all the district boundaries centered on a state:
Display all the district boundaries centered on a state and highlight one district:
The next three example maps show the congressional district boundaries for a single state or only the boundary for a single district. This type of map will generally be more useful since you can zoom in much more. These maps display medium resolution and high resolution data.
Display the district boundaries for a single state:
Display the district boundaries for a single state and highlight one district:
Display the district boundaries for a single district:
You can also make a custom map link that specifies the map center and zoom level that will be used when the map opens. Start by making the map look on your screen the way you want the map to look when it opens. Then click Menu ==> Link to this map. Notice that the map link that is displayed includes an ll parameter (map center) and z parameter (zoom). Here is the documentation on the link parameters that Gmap4 understands.
Reminder: If the map link does not include an ll and z parameter then when the map opens it will automatically be centered and zoomed based on the value of the congress parameter.
About the Data
The data for the congressional district boundaries comes from the U.S. Census Bureau where it is hosted on a GIS (Geographical Information System) server. That data has been downloaded as KMZ files which are hosted on the MappingSupport.com server. Most of the time the map is displaying one or two KMZ files. If you zoom in to level 13 or higher then the congressional district boundaries appear as two-tone yellow and red lines. The data for these two-tone lines comes directly from federal GIS servers to your screen. Those servers are operated by the USGS (The National Map) and NOAA/BOEM (Marine Cadastre project). Be patient. It might take a few seconds for the yellow and red district lines to appear on your screen depending on how much other work those servers are doing.
The data that appears in the popup when you click on a congressional district was developed with custom code that was produced as part of this project. That code examined the web page for each elected person and located their social media links.
The congressional district map is displayed by Gmap4 which is a general purpose enhanced Google map viewer developed by Joseph Elfelt. Gmap4 can be used for any non-commercial purpose.
For more information you can visit the Gmap4 homepage which has a FAQ, list of features, lots of example map links, quick start info (on the Help page) and more.
News about Gmap4 first appears on the Gmap4 Facebook page.
Qustions can be emailed via the Gmap4 contact page.