Cities and counties across the country are racing to prepare residents for the 2020 census. One of the most helpful preparation tools has been using a data map to track which neighborhoods will likely be difficult to count based on past census information.

The Hard to Count 2020 Census Map, created by the City University of New York’s Mapping Service, is an interactive online map that shows local areas that are considered “hard to count communities”—neighborhoods where census participation rates are the lowest. This number is mainly based on the self-response mail-in rates to the census, which is considered the most accurate reflection of census participation.

The map was mainly designed as a census outreach resource for local agencies, but it is open and free to use by the public. Anyone can find out how their neighborhood performed in the past census using the map; simply zoom in any area in the U.S. based on the area tract, local address, legislative or congressional district, and ZIP code.