L2’s Zip-to-District Tables

L2’s zip-to-district tables can be used to identify the congressional district, state senate district and state house district assigned to a particular address based on an analysis of its zip code.  While not as precise as an analysis of the full address, this method can still prove useful. 

Match Files for Current Official Districts

The tables found in this directory consist of three sets for each district type for a total of nine tables.  One set analyzes the relationship between five-digit zip codes and the district in question.  A second set does the same for zip+2 and the third set analyzes assignments based on the full zip+4 zip code.

The structure of each table is the same.

The first three columns identify the state, the district number and the county FIPs code.  The fourth column will show the 5-digit zip.  (Note that in the zip7 or zip9 tables the fifth column will show either the 2-digit or the 4-digit extension, depending on the table type).  The fifth column shows the total number of voters associated with the specified district in that zip code while the sixth column shows the total voter count (regardless of district assignment) in the zip.  Finally, the seventh column shows the percentage of the voters within that zip who are found in the specified district. 

The table shown above is an analysis of the 5-digit zip 99502 in Alaska.  There are two rows for this particular zip.  The first row shows that 74.5% of the voters in that zip code are assigned to state house district 22 while 25.2% are assigned to state house district 21.  In the case of a split zip such as this, it may be the case that some small percentage of the voters might be found in one or more districts not listed.  L2 shows rows only for the districts assigned to 10% or more of the voters in that zip code.  In the case of the zip+2 and zip+4 tables, you will find fewer and fewer cases where there are multiple rows for the same zip entry.  This is because the zip+2 and zip+4 geographical areas are smaller and far less likely to contain multiple districts.  Nearly all of those will show that the entry is 100% in the specified district.

Using these tables is straightforward.  When performing a match against your address file, start by matching from the zip+4 table which is the most precise and for which most zip+4s are 100% within a single district.  For the records that do not find a match, try the zip+2 table.  Finally, for the remaining unmatched records, match against the 5-digit zip table.  You may decide when using any of these tables to limit your matches only to rows showing 100% of that zip to be in the assigned district, thus possibly lowering your match rate but increasing the accuracy of the match.

Note that zip codes are regularly updated by the Post Office so these tables will be updated approximately every two weeks.

Note as well that if your file contains P.O. boxes, the district assignment will be based on the location of the Post Office rather than where the individual actually lives and may result in false assignments.  Make sure that the addresses you are matching are residence (rather than mailing) addresses to avoid this problem.

Also note that this method of district assignment cannot be expected to be 100% accurate.  Because of irregularities in zip code assignments, it is possible that a very small percentage of records will be misassigned using this technique.

Finally, note that one folder contains tables for every state and the district assignments are those that are in effect just prior to the 2020 census redistricting.  The second folder contains tables only for the states that have finalized their 2020 census redistricting and for which L2 has matched the new data into its files.  That list of states will grow over time.

Match Files for Historical District Boundaries

The Zip-To-District match files that use the current, official district boundaries are located in the folder named Match Files for Current Official Districts.  You will also find a separate folder named Historical Archive, which contains two additional sets of files.

The first of these, Match Files for Districts From the 2010 Census, contains files that match Zip, ZipPlus2, and ZipPlus4 to the historical US Congressional, State House, and State Senate districts which were in effect from 2011 until 2022.  Just like with the match files for currently existing districts, these 2010 Census files contain the zip-to-district match data for all 50 states plus the District of Columbia.  This set of match files employs a structure that is identical to the match files for current districts described above.  They are to be used only for applications that require matching addresses to the historical district boundaries that are the predecessors of the current official districts.

The second set of files located in the Historical Archive are the Match Files for 2023 Districts.  A small number of states (listed below) experienced changes to their US Congressional, State House, and/or State Senate district boundaries in 2024 due to legal challenges.  For these states only, the Match Files for 2023 Districts folder contains zip-to-district match files for the district boundaries that went into effect in 2022 and were replaced by the current official boundaries in 2024.

• The states with 2023 US Congressional Districts are AL, GA, LA, NC and NY.
• The states with 2023 State House Districts are GA, MI, NC, NY, OH, SC, WA and WI.
• The states with 2023 State Senate Districts are GA, KS, NC, OH, SC, WA and WI.

Please note that the match files in this 2023 Districts folder for US Congressional districts only feature the Zip, ZipPlus2, and ZipPlus4 data for the states that underwent changes in their US Congressional district boundaries in 2024, and likewise for State House and State Senate districts.  For example, the Zip codes of Alabama addresses will not be present in the match files for 2023 State House Districts or 2023 State Senate Districts.

Again, the two sets of files in the Historical Archive are based on historical district boundaries, in contrast with the current official district boundaries. As such, these files are not to be used as a basis for matching addresses to the current official district boundaries. Only use the files found in the Match Files for Current Official Districts folder to match addresses to current districts.