Congressional and Legislative districts are created using census geography. This is because, by law, districts must be based on census population figures. At the bottom end, those figures correspond with small tabulation areas called census blocks. Districts are, in essence, aggregations of census blocks. Each one of the 232,403 census blocks in the state is assigned to a State House, State Senate, and Congressional district. If we know what census block a person lives in, we know what their districts are.
So the question becomes, how do we know what census block a person lives in? The short answer is that the U.S. Postal Service publishes correspondence files that allow us to link ZIP+4 codes with census blocks. The caveats are that:
- Census geography is not perfect. The Census Bureau has a very large digital map of the state with over a million street segments. If the Postal Service cannot reconcile a particular address with current census geography, it’s ZIP+4 code is not included in their correspondence file.
- The Postal Service’s ZIP+4 codes are constantly being updated as new houses are built, new streets put in, etc. They only go through the process of reconciling their codes with census geography every few years, so there is a lag between the time new codes are assigned and when they show up in our database.
The Legislature communicates district configurations to the State Board of Elections, who in turn works with local boards of elections to get voters properly assigned. Local boards of elections are often able to come up with the best address locations since they are familiar with their areas. The geography maintained by local governments tends to be the most accurate available. You may want to contact them directly. The State Board of Elections maintains a list of contact information for all 100 county boards of elections in North Carolina.
District assignments are generally available via the State Board of Elections' "Voter Lookup" tool. In preparation for the upcoming elections however, those district assignments are currently being updated to the new districts. While the new assignments are important for voting, they cannot be used to identify your current representatives.