1. Data
  2. CT Parcels

CT Parcels

Parcels, or defined pieces of land, delineate how land is divided. Parcels are the key mapping unit for town operations including assessment, public safety, permitting and more.

Parcel Map Layers

In Connecticut, parcels are maintained at the local level (town or city) in different ways. Some municipalities have GIS staff who maintain parcels. Some Councils of Governments (COGs) maintain parcels for their member towns and some towns hire consultants. Every town in Connecticut has digital parcels. Most have an online viewer so that citizens can view and explore the map layers.

In 2018, Public Act 18-175, section 6 was passed and requires each municipality to submit a digital parcel file and some assessment information each year to the Council of Governments (COGs) to which it belongs. The Office of Policy and Management (OPM) subsequently asks the COGs to share the files so they can be made available for download in one location on the CT Geodata Portal maintained by the CT GIS Office. The ability to download all of the municipal parcels from OPM (before the GIS Office was established) made it possible for CT ECO to create a the first single parcel service based on 2020 town parcel datasets. After the establishing of the CT GIS Office, a first task was to create a workflow to aggregate all of the town parcels including their polygon shapes and tabular information about each parcel, into a single, queryable layer.

Quick Links

Parcel Viewer on CT Geodata Portal
Most recent parcels by town and COG

Parcel Viewer on CT ECO
Includes all parcel datasets

Parcel page on the CT Geodata Portal
All about CT Parcel layers

CT GIS Office Aggregated Parcel Dataset

Following the 2023 parcel data collect, the CT GIS Office aggregated the parcels, including their geometry (shapes) and attribute information (table) for more standardized CAMA (Computer-Assisted Mass Appraisal) data which is maintained by municipalities. This was a first for Connecticut and allowed for querying, filtering, and searching parcels based on a variety of criteria. The statewide dataset continues to improve with each annual collect thanks to cooperation from municipalities and COGs and improved workflows at the CT GIS Office. The CT GIS Office maintains a Parcels page within the CT Geodata Portal that includes more information and details.

Each year, the parcel  layer (called Connecticut CAMA and Parcel Layer) is updated. The layer from the pervious year is saved and named with its year, such as Connecticut CAMA and Parcel Layer 2024 and Connecticut CAMA and Parcel Layer 2023.

Aside from information and the parcel services, the CT GIS Office also provides a Connecticut Parcel Viewer for exploring the parcels and their attributes.

The Role of CT ECO

CT ECO is sharing and promoting the parcel information because of it's high value for many applications across the state. CT ECO also provides information, background, and resources about the parcels and how to use the datasets. Before 2024, the CT ECO service and viewer were the only ways to view and access all of the town parcels in one place. Now, the CT GIS Office provides the information annually. CT ECO simply shares the information and has no involvement in the creation or editing of the datasets including tabular information.

Connect to Parcel Services

The first step in connecting to services is finding the services. Most parcel services can be found on the CT Geodata Portal.

  1. Visit the CT Geodata Portal Data Library and search for parcels (direct link)
  2. On the left, select Feature Service to filter the results to show only services. (direct link)
  3. The most updated layer is called Connecticut CAMA and Parcel Layer. It is updated each year and we will use it as the example here.
  4. Click Full Details to open the about page for the Connecticut CAMA and Parcel Layer.
  5. Scroll down and locate View Data Source to open the link used to connect to the service.

Add Parcel Layers to the Web Map from ArcGIS Online

To add a parcel service (or any service for that matter) to a web map in ArcGIS Online using ArcGIS Online registered services:

  1. In the ArcGIS Online Map Viewer, click on Add and then Browse for Layers.
  2. Change from My content to ArcGIS Online.
  3. Type CT Parcels or similar in the Search box.
  4. Scroll through the list of services and click +Add to add the desired service(s) to the web map. Note the publisher name to ensure that it is the correct service from a reputable publisher. For example, CT Geodata Portal services are usually published by State of Connecticut, or similar. CT ECO services are published by a CT ECO account or accounts that start with UConnCTECO.

Add Parcel Layers to the Web Map from Server URL

To add any parcel service (or any service for that matter) to a web map in ArcGIS Online using the service URL:

  1. In the ArcGIS Online Map Viewer, click Add and then Add Layer from URL.
  2. In the Add Layer box under URL, paste the service link (see steps and links above).
  3.  Click the button Add to map. There are many options for a feature service in the web map including symbology, filtering, custom pop-ups, and much more.

    Download Parcel Data

    Download CT parcel data from the CT Geodata Portal Parcels Homepage by selecting Download Data, expanding the desired dataset, and clicking on the download link.

    Parcels from the 2020 Data Collect on CT ECO (2020)

    Parcels from the 2020 Data Collect on CT ECO

    Once all COGs had delivered their member town parcels to OPM in 2020, CT ECO folks downloaded the files with the goal of creating a single service of all parcels in Connecticut. In order to preserve the attributes, or the information about each parcel, the team decided to keep each towns dataset separate but put them together into one service. This was necessary because towns use all different names and naming conventions for the data making it difficult and time consuming to aggregate. By keeping them separate, the pop-ups in the viewer could still show the attributes and subsequent information for each parcel in each town. Vast differences in the pop-ups is due to vast differences in the data provided.

    CT Parcels Viewer (include the 2020 parcel layer)
    CT Parcel Services (2020)

    Some information about the attributes and codes in the 2020 parcel datasets are available in the 2020 parcels report.

    Parcels from the Protected Open Space Mapping (POSM) Project (2003-2010)

    Parcels from the Protected Open Space Mapping (POSM) Project (2003-2010)

    For a long time the only "statewide" parcel service was created through the Department of Energy and Environmental Protection's (DEEP) Protected Open Space Mapping (POSM) project. Parcels were necessary in order to catalog and map Open Space. The POSM parcel layer is described in the CT ECO Resource Guide which explains how it is a combination of parcels collected from municipalities with creation dates ranging from 2003 to 2010. This layer was not updated and not all towns contributed.

    Parcels from POSM: Resource Guide, Data Guide, Metadata, Map Service
    POSM: Resource Guide, Data Guide, Metadata, Map Service

    Parcel FAQs

    Q. What are the difficulties in merging the town parcel files together into a statewide layer?

    Q. What are the difficulties in merging the town parcel files together into a statewide layer?

    A. There are multiple reasons, all stemming from the fact they are all done differently and therefore don't easily "fit" together.

        1. Town Boundaries. There is no accurate, authoritative town boundary layer for Connecticut which leads to overlaps and gaps along town boundaries across the state.

    These are a few of the many examples showing the issues at town boundaries (black lines).The colors are different town's parcels. Notice (1) town boundaries don't line up with the town parcels, (2) there are overlaps in neighboring town parcel datasets and (3) there are gaps in neighboring town parcel datasets. .

        2. They have different attributes. Attributes are the information in the table behind the geographic parcel polygons. For example, even though most town datasets include Map, Block, Lot information, they are listed in many different ways.

    Examples of same information (Map, Block and Lot) stored in the tables of town parcel GIS layers. There are all sorts of combinations and ways that the information is stored in the table which makes it difficult and complicated to combine in a meaningful way. And this is just for Map, Block and Lot. The same complication exists for IDs, addresses and pretty much everything else.

        3. Town boundaries. There is not an accurate, authoritative town boundary layer for Connecticut. Parcels that cross town boundaries are sometimes "cut" in the mapping layer or sometimes exist in multiple towns. It is a mess and could be improved by (1) an accurate town boundary layer that is used by all municipalities and (2) data standards so that municipal parcels are all created and maintained under the same set of guidelines.

    Q. What are the little squares and circles? They are clearly not big enough to be a real parcel, are they?

    Q. What are the little squares and circles? They are clearly not big enough to be a real parcel, are they?

    A. The little circles and little squares are two of the ways that municipalities handle single parcels with multiple owners. Other ways include repeating the parcel multiple times on top of itself, one for each owner (one case had over 300 polygons stacked on top of itself!) and "cutting" the building footprints out of the larger parcel.

    Q. What should I do if I find an error in the parcel data?

    Q. What should I do if I find an error in the parcel data?

    A. Contact the municipality.