1. Zip code boundaries change, in ways small and large - these are not a stable analysis unit. Data you received keyed to zip codes may have used an earlier and very different boundary for your zip codes of interest.
2. Historically, the United States Postal Service has not published zip code boundaries, and instead, boundary datasets are compiled by third party vendors from address data. That means that the boundary data are not authoritative, and any data you have keyed to zip codes may use a different, vendor-specific method for generating boundaries from the data here.
3. Zip codes are designed to optimize mail delivery, not social, environmental, or demographic characteristics. Analysis using zip codes is subject to create issues with the Modifiable Areal Unit Problem that will bias any results because your units of analysis aren't designed for the data being studied.

This is a MD iMAP hosted service. Find more information at http://imap.maryland.gov. In 1993 - the Maryland Department of Planning and the Maryland State Highway Administration entered into a Data Base Usage Agreement with Bell Atlantic and Data Chromatics - Inc. to develop an enhanced street address map for Maryland. ZIP Code boundary area files were one of the products derived from this partnership. The resulting boundary area files were intended to improve the cartographic quality and accuracy of the ZIP code boundary area files derived from the U.S. Census Bureau's post 1990 Census TIGER\Line Files (based on the Census Bureau's ZIP code tabulation areas - ZCTAs). Subsequent iterative improvements to the ZIP Code boundary area files have been made using premise address information associated with mapped parcel records as provided in the Maryland Department of Planning's MdProperty View GIS tax map and parcel record DVD product. The resulting files are meant to serve as a good approximation"" of ZIP codes as polygons (which in reality they are not) but are not official ZIP Code maps and are not meant to be a substitute for any products offered by the U.S. Postal Service - the official source for ZIP code information. While there are no restrictions on their use we do recommend that they are best used with MdProperty View and that MDP makes no guarantee or warranty regarding the files. Last Updated: 2012Feature Service Link:https://mdgeodata.md.gov/imap/rest/services/Boundaries/MD_PoliticalBoundaries/FeatureServer ADDITIONAL LICENSE TERMS: The Spatial Data and the information therein (collectively the ""Data"") is provided "as is" without warranty of any kind either expressed implied or statutory. The user assumes the entire risk as to quality and performance of the Data. No guarantee of accuracy is granted nor is any responsibility for reliance thereon assumed. In no event shall the State of Maryland be liable for direct indirect incidental consequential or special damages of any kind. The State of Maryland does not accept liability for any damages or misrepresentation caused by inaccuracies in the Data or as a result to changes to the Data nor is there responsibility assumed to maintain the Data in any manner or form. The Data can be freely distributed as long as the metadata entry is not modified or deleted. Any data derived from the Data must acknowledge the State of Maryland in the metadata.

Census ZIP Code Tabulation Areas This feature layer, utilizing National Geospatial Data Asset (NGDA) data from the U.S. Census Bureau (USCB), displays ZIP Code Tabulation Areas in the United States. Per the USCB, “ZIP Code Tabulation Areas (ZCTAs) are approximate area representations of U.S. Postal Service (USPS) ZIP Code service areas that the Census Bureau creates to present statistical data for each decennial census. Data users should not use ZCTAs to identify the official USPS ZIP Code for mail delivery. The USPS makes periodic changes to ZIP Codes to support more efficient mail delivery.” Tabulation Area: 90210 Data currency: This cached Esri federal service is checked weekly for updates from its enterprise federal source (ZIP Code Tabulation Areas) and will support mapping, analysis, data exports and OGC API – Feature access.NGDAID: 58 (Series Information for 2020 Census 5-Digit ZIP Code Tabulation Area (ZCTA5) National TIGER/Line Shapefiles, Current)OGC API Features Link: (Census ZIP Code Tabulation Areas - OGC Features) copy this link to embed it in OGC Compliant viewersFor more information, please visit: ZIP Code Tabulation Areas (ZCTAs)For feedback please contact: Esri_US_Federal_Data@esri.comThumbnail source: Esri BasemapsNGDA Data Set This data set is part of the NGDA Governmental Units, and Administrative and Statistical Boundaries Theme Community. Per the Federal Geospatial Data Committee (FGDC), this theme is defined as the “boundaries that delineate geographic areas for uses such as governance and the general provision of services (e.g., states, American Indian reservations, counties, cities, towns, etc.), administration and/or for a specific purpose (e.g., congressional districts, school districts, fire districts, Alaska Native Regional Corporations, etc.), and/or provision of statistical data (census tracts, census blocks, metropolitan and micropolitan statistical areas, etc.). Boundaries for these various types of geographic areas are either defined through a documented legal description or through criteria and guidelines. Other boundaries may include international limits, those of federal land ownership, the extent of administrative regions for various federal agencies, as well as the jurisdictional offshore limits of U.S. sovereignty. Boundaries associated solely with natural resources and/or cultural entities are excluded from this theme and are included in the appropriate subject themes.” For other NGDA Content: Esri Federal Datasets

The City of Austin provides this zip code dataset for general use, designed to support a variety of research and analysis needs. Please note that while we facilitate access to this data, the dataset is owned and produced by the United States Postal Service (USPS). Users are encouraged to acknowledge USPS as the source when utilizing this dataset in their work. U.S. ZIP Code Areas (Five-Digit) represents five-digit ZIP Code areas used by the U.S. Postal Service to deliver mail more effectively. The first digit of a five-digit ZIP Code divides the United States into 10 large groups of states numbered from 0 in the Northeast to 9 in the far West. Within these areas, each state is divided into an average of 10 smaller geographical areas, identified by the second and third digits. These digits, in conjunction with the first digit, represent a sectional center facility or a mail processing facility area. The fourth and fifth digits identify a post office, station, branch or local delivery area. This product is for informational purposes and may not have been prepared for or be suitable for legal, engineering, or surveying purposes. It does not represent an on-the-ground survey and represents only the approximate relative location of property boundaries. This product has been produced by the City of Austin for the sole purpose of geographic reference. No warranty is made by the City of Austin regarding specific accuracy or completeness. City of Austin Open Data Terms of Use: https://datahub.austintexas.gov/stories/s/ranj-cccq

Zip Codes (5-digit). The dataset polygons represent location and attributes of zip codes, created as part of the DC Geographic Information System (DC GIS) for the D.C. Office of the Chief Technology Officer (OCTO) and participating D.C. government agencies. Zip Codes were identified from public records (US Postal Service) and created selecting arcs from the street centerlines and vector property map.

The dataset represents approximate Zip code boundaries in Westchester County. Data was downloaded from the U.S. Census Bureau 2020. The cartographic boundary files are simplified representations of selected geographic areas from the Census Bureau’s MAF/TIGER geographic database. These boundary files are specifically designed for small-scale thematic mapping. Some of the boundaries near CT were edited to match the state line. This is NOT official Postal Service data. The data was updated in August 2025.

This dataset contains all zip codes in Montgomery County. Zip codes are the postal delivery areas defined by USPS. Zip codes with mailboxes only are not included.

https://gis3.montgomerycountymd.gov/arcgis/rest/services/general/zipcode/MapServer/0

This web map presents five-digit ZIP Code areas used by the U.S. Postal Service to deliver mail more effectively. The first digit of a five-digit ZIP Code divides the United States into 10 large groups of states numbered from 0 in the Northeast to 9 in the far West. Within these areas, each state is divided into an average of 10 smaller geographical areas, identified by the second and third digits. These digits, in conjunction with the first digit, represent a sectional center facility or a mail processing facility area. The fourth and fifth digits identify a post office, station, branch or local delivery area. It provides area, post office name, and population for each ZIP Code area in the United States.The ZIP Code boundaries are from 2024. The population estimates are from Esri Demographics.

5-Digit and 3-Digit ZIP Code data for Maptitude mapping software are from Caliper Corporation and contain boundaries and demographic data.

This data represents five-digit ZIP Code areas used by the U.S. Postal Service. This is an ArcGIS Online item directly from Esri. For more information see https://www.arcgis.com/home/item.html?id=8d2012a2016e484dafaac0451f9aea24.

This dataset identifies selected economic characteristics by zip code tabulation areas within the United States. This dataset resulted from the American Community Survey (ACS) conducted from 2010 through 2014. The economic characteristics include employment status, commuting to work, occupation, class of worker, income and benefits, health insurance coverage, and percentage of families and people whose income in the past 12 months is below the poverty level.

View full metadata https://www.cambridgema.gov/GIS/gisdatadictionary/Boundary/BOUNDARY_Zipcodes

Description This Polygon layer contains the boundaries of the five United States Postal Service (USPS) ZIP code areas in the city of Cambridge.

About Edit Dates This data is automatically updated on a set schedule. The Socrata edit date may not reflect the actual edit dates in the data. For more details please see the update date on the full metadata page or view the edit date within the data rows.

Abstract

A crosswalk dataset matching US ZIP codes to corresponding county codes

Documentation

The denominators used to calculate the address ratios are the ZIP code totals. When a ZIP is split by any of the other geographies, that ZIP code is duplicated in the crosswalk file.

**Example: **ZIP code 03870 is split by two different Census tracts, 33015066000 and 33015071000, which appear in the tract column. The ratio of residential addresses in the first ZIP-Tract record to the total number of residential addresses in the ZIP code is .0042 (.42%). The remaining residential addresses in that ZIP (99.58%) fall into the second ZIP-Tract record.

So, for example, if one wanted to allocate data from ZIP code 03870 to each Census tract located in that ZIP code, one would multiply the number of observations in the ZIP code by the residential ratio for each tract associated with that ZIP code.

https://redivis.com/fileUploads/4ecb405e-f533-4a5b-8286-11e56bb93368%3E" alt="">(Note that the sum of each ratio column for each distinct ZIP code may not always equal 1.00 (or 100%) due to rounding issues.)

County definition

In the United States, a county is an administrative or political subdivision of a state that consists of a geographic region with specific boundaries and usually some level of governmental authority. The term "county" is used in 48 U.S. states, while Louisiana and Alaska have functionally equivalent subdivisions called parishes and boroughs, respectively.

Further reading

The following article demonstrates how to more effectively use the U.S. Department of Housing and Urban Development (HUD) United States Postal Service ZIP Code Crosswalk Files when working with disparate geographies.

Wilson, Ron and Din, Alexander, 2018. “Understanding and Enhancing the U.S. Department of Housing and Urban Development’s ZIP Code Crosswalk Files,” Cityscape: A Journal of Policy Development and Research, Volume 20 Number 2, 277 – 294. URL: https://www.huduser.gov/portal/periodicals/cityscpe/vol20num2/ch16.pdf

Contact information

Questions regarding these crosswalk files can be directed to Alex Din with the subject line HUD-Crosswalks.

Acknowledgement

This dataset is taken from the U.S. Department of Housing and Urban Development (HUD) office: https://www.huduser.gov/portal/datasets/usps_crosswalk.html#codebook

US Census Bureau ZIP Code Tabulation Areas (ZCTAs) found within or partially within the borders of the City of Detroit. ZCTAs are a geographic product of the U.S. Census Bureau created to allow mapping, display, and geographic analyses of the United States Postal Service (USPS) Zone Improvement Plan (ZIP) Codes dataset. They are areal representations of ZIP Codes, and not all ZIP Codes are represented by ZCTAs (for example, ZIP Codes associated with PO Boxes). For a list of all ZIP Codes within or partially within the borders of the City of Detroit, please refer to our City of Detroit USPS Zone Improvement Plan (ZIP) Codes dataset.More information on ZCTAs, and how they differ from ZIP Codes, can be found on the US Census Bureau's website.

The 2019 cartographic boundary shapefiles are simplified representations of selected geographic areas from the U.S. Census Bureau's Master Address File / Topologically Integrated Geographic Encoding and Referencing (MAF/TIGER) Database (MTDB). These boundary files are specifically designed for small-scale thematic mapping. When possible, generalization is performed with the intent to maintain the hierarchical relationships among geographies and to maintain the alignment of geographies within a file set for a given year. Geographic areas may not align with the same areas from another year. Some geographies are available as nation-based files while others are available only as state-based files. ZIP Code Tabulation Areas (ZCTAs) are approximate area representations of U.S. Postal Service (USPS) ZIP Code service areas that the Census Bureau creates to present statistical data for each decennial census. The Census Bureau delineates ZCTA boundaries for the United States, Puerto Rico, American Samoa, Guam, the Commonwealth of the Northern Mariana Islands, and the U.S. Virgin Islands once each decade following the decennial census. Data users should not use ZCTAs to identify the official USPS ZIP Code for mail delivery. The USPS makes periodic changes to ZIP Codes to support more efficient mail delivery. The Census Bureau uses tabulation blocks as the basis for defining each ZCTA. Tabulation blocks are assigned to a ZCTA based on the most frequently occurring ZIP Code for the addresses contained within that block. The most frequently occurring ZIP Code also becomes the five-digit numeric code of the ZCTA. These codes may contain leading zeros. Blocks that do not contain addresses but are surrounded by a single ZCTA (enclaves) are assigned to the surrounding ZCTA. Because the Census Bureau only uses the most frequently occurring ZIP Code to assign blocks, a ZCTA may not exist for every USPS ZIP Code. Some ZIP Codes may not have a matching ZCTA because too few addresses were associated with the specific ZIP Code or the ZIP Code was not the most frequently occurring ZIP Code within any of the blocks where it exists. The generalized ZCTA boundaries in this file are based on those delineated following the 2010 Census.

This feature layer displays Affordable Connectivity Plan (ACP) eligibility data provided by USAC and the Census Bureau's American Community Survey 5 Year Tables for 2017-2021. The data is shown for 2020 U.S Census Boundaries (2022 Dataset) clipped to WA State.

Dataset Card for Zip Code to Timezone Offset Mapping

This dataset maps Zip Codes and Postal Codes for the USA and Canada to the relevant timezone offset.

  Dataset Details





  Dataset Description

In addition to providing a mapping from a Zip Code or Postal Code to timezone offset, it also contains the timezone offset for DST (if observed).

Curated by: Bobby Gill, BlueLabel

  Acknowledgements

Based off the Work Here:… See the full description on the dataset page: https://huggingface.co/datasets/omgbobbyg/Zip-Code-to-Timezone.

Layered datasets for 1-digit, 2-digit, 3-digit (SCF) ZIP prefixes and Areas without ZIP Coverage.

This American Community Survey (ACS) data set identifies the language spoken at home by zip code tabulation area within the United States, from 2012 through 2016. The dataset identifies languages spoken and how well English is spoken by Zip Code Tabulation Area.

This study includes the number of public transit stops per United States census tract or ZIP code tabulation area (ZCTA) based on data from the National Transit Map (NTM). Each observation represents the count and density (per capita and square mile) of transit stops within a census tract or ZIP code tabulation area (ZCTA), as voluntarily reported to NTM between 2016-2018 and 2024 by one of 270 regional transit agencies choosing to participate.