B Find Connecticut Data

TODO: Rewrite and update this appendix

Since this book was created in Hartford, Connecticut, we include state and municipal open data repositories and boundary files.

Connecticut Open Data (http://data.ct.gov), the official portal for state government agencies, is hosted on the Socrata platform, which offers built-in data visualization tools and APIs. See also how to create a filtered point map with Socrata in this book.

See also separate repositories for individual state agencies:

Connecticut State Data Center (http://ctsdc.uconn.edu/), part of the U.S. Census Data Center Network, is the lead agency for US Census data and other socioeconomic data for Connecticut, and is based at the University of Connecticut Libraries. The site also features data visualizations created on the Tableau platform and provides population projections for the state of Connecticut.

MAGIC: The Map and Geographic Information Center (http://magic.lib.uconn.edu), based at the University of Connecticut Libraries, specializes in providing geographic, aerial photography, and map images for the state, past and present. The site also features interactive maps.

DataHaven (http://ctdatahaven.org/), a non-profit organization, collects and interprets information about Connecticut neighborhoods, such as its Community Wellbeing Survey. Data resources feature neighborhood profiles for densely-populated areas (New Haven and Hartford-West Hartford), and town profiles for other areas across the state.

Connecticut Data Collaborative (http://ctdata.org) is a public-private partnership that advocates for open data access to drive planning, policy, budgeting and decision making in Connecticut at the state, regional and local levels. We democratize public data through custom data exploration tools and a dynamic town profile tool, hosted on the open-source CKAN platform. Users can find state and federal data on topics such as public health, education, crime, municipal data, and racial profiling data.

Hartford Data (http://data.hartford.gov), the official portal of the City of Hartford municipal government, is hosted on the Socrata platform, which features built-in visualizations and APIs. See also how to create a filtered point map with Socrata in this book. Also, the Hartford Data site links to the City’s ArcGIS Online geographic data (http://gisdata.hartford.gov/) and the City’s financial data (http://checkbook.hartford.gov/) and budget (http://budget.hartford.gov/).

In addition to the official repositories above, Connecticut news organizations that create data visualizations often include links to download data files.

Connecticut Mirror / Trend CT (http://ctmirror.org/) and (http://trendct.org/) are publications of the Connecticut News Project, an independent, nonpartisan, nonprofit organization that focuses on state policy issues. Most of their data visualizations are built with open-source code, with publicly accessible data files. See also their GitHub repository (https://github.com/trendct).

Hartford Courant Data Desk (http://www.courant.com/data-desk) produces digital visualizations for the Hartford Courant, the largest daily newspaper in Connecticut, owned by Tribune Publishing. Many of these data visualizations are published on the Tableau platform, which allows readers to download the underlying data.

Census areas in the Hartford region

The U.S. Census Bureau collects and shares population, housing, and economic data on its open repositories.

  • The Decennial Census is a full count of the population every ten years, most recently in 2010 and the upcoming one in 2020. Because decennial data are counts and not estimates, they represent “true” values and hence come without margins of errors.
  • The American Community Survey (ACS) (https://www.census.gov/programs-surveys/acs/) is annual sample count, which produces:
    • 1-year estimates for areas with populations of 65,000+
    • 5-year estimates for all census areas
    • ACS used to release 3-year estimates for geographies with population of 20,000+, but discontinued after the 2011-2013 release.

Because ACS produces estimates and not “true” counts, data comes with margins of errors. Generally, margins of errors are higher for smaller geographies (eg census blocks) and smaller values (eg the number of Asian females aged 60+ who live in Union, CT). Hence, one needs to be critical when using ACS or other survey data.


Data.census.gov (https://data.census.gov) is the main platform to access US Census data. It provides an easy search across census and survey tables. There is an interface to view tables for various years and geographies, and a download button to save data as CSV or PDF. It replaced American FactFinder (https://factfinder.census.gov) in July 2019.

Social Explorer

Social Explorer (https://www.socialexplorer.com/) is a popular tool to view and download census and related demographic data, past and present. The platform allows users to create data maps that may be exported as static images or presentation slides. Social Explorer requires subscription, but many academic institutions provide access.

TODO: create tutorial on how to cleanly download census data from Social Explorer and Census.gov to join with geography, especially census tract numbers

See also Bulk Geocode with the US Census Geocoder and find GeoIDs (such as the census tract) for each address.

National Center for Education Statistics

National Center for Education Statistics (NCES) (https://nces.ed.gov/) is the primary federal agency for collecting and reporting education data.

  • Elementary/Secondary Information System (ELSi) (https://nces.ed.gov/ccd/elsi) - create custom tables and charts from the Common Core of Data (CCD) and Private School Survey.


  • Converted from shapefile WGS84 to GeoJSON format
  • To download a GeoJSON file, right-click the link and Save to your computer
  • If you accidentally open the GeoJSON code in your browser, select File > Save Web Page to download it
  • To view or edit, drag files into http://geojson.io or http://mapshaper.org
  • Learn more in the Transform Your Map Data chapter of this book
Geography Year-Source-Size Right-click + Save to download GeoJSON
CT outline 2010 Census UConn MAGIC WGS84 1:100,000 ct-outline.geojson
CT counties 2010 Census UConn MAGIC WGS84 1:100,000 ct-counties.geojson
CT towns 2010 Census UConn MAGIC WGS84 simplified to 224k ct-towns.geojson
CT census tracts 2010 Census UConn MAGIC WGS84 1:100,000 ct-tracts-2010.geojson
Hartford County outline 2010 Census UConn MAGIC WGS84 1:100,000 hartfordcounty-outline.geojson
Hartford County towns 2010 Census UConn MAGIC WGS84 1:100,000 hartfordcounty-towns.geojson
Hartford County tracts 2010 Census UConn MAGIC WGS84 1:100,000 hartfordcounty-tracts-2010.geojson
Hartford outline 2010 Census UConn MAGIC WGS84 1:100,000 hartford-outline.geojson
Hartford census tracts 2010 Census UConn MAGIC WGS84 1:100,000 hartford-tracts-2010.geojson
Hartford neighborhoods 2015 Hartford Open Data 1:50,000 hartford-neighborhoods.geojson

TODO: - add Capitol Region Council of Governments (CRCOG) http://www.crcog.org/ - add school districts (and clarify elementary-secondary) - add Capitol Region Education Council (CREC) http://www.crec.org/ - add school attendance areas from federal site - describe Freedom of Information Act (FOIA) data requests in Connecticut