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.
Background: Parcel Map Layers in Connecticut
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 voluntarily share the files so they can be made available for download in one location on the OPM website, now within the State GIS Office. The ability to download all of the municipal parcels made it possible for CT ECO to create a single parcel service based on 2020 town datasets and the CT GIS Office to actually aggregate parcels, including their shapes and attributes, into a single layer.
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 for more standardized CAMA (Computer-Assisted Mass Appraisal) data which is maintained by municipalities. This is a first for Connecticut and allows for querying, filtering, and searching for parcels based on a variety of criteria.
CT Parcel Information page on the CT Geodata Portal which includes the Connecticut State Parcel Layer (2023)
- data download by COG or statewide,
- service on the CT Geodata Portal, and
- viewer on the CT Geodata Portal.
Parcels from the 2020 Data Collect on CT ECO (2020)
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 (2020)
CT Parcel Services (2020)
Town by town parcel download of 2020 shapefiles after CT ECO clean-up
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
The Role of CT ECO
CT ECO is publishing the parcel information downloaded directly from OPM 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, without the CT ECO service and viewer, the parcel layers were only available in individual town viewers or for download in GIS format which require software and know-how to view and use. CT ECO simply shares the information and has no involvement in the creation or editing of the datasets including tabular information.