Connecticut Census Tract Boundaries are Changing

In February 2021, the U.S. Census Bureau updated census geographic boundaries for many states across the country, including Connecticut. Since data from both the American Community Survey and decennial census is often consumed at the census-tract level (areas of up to 4,000 people), it is important for data users to understand the differences between 2010 and 2020 boundaries, as new data will be disseminated using updated boundaries going forward.

For a summary of changes by town, scroll to the bottom of this blog post.

What changed in Connecticut?

• The total number of census tracts in Connecticut increased by 50, from 833 in 2010 to 883 in 2020.
• Of the 883 census tracts, 773 maintained their geographic ID, and 110 have a new geographic ID. The new ID is often assigned when a census tract becomes overcrowded, and as a result is divided into several tracts. For example, Hartford's tract 5031 (in 2010 division) was split into 5031.01 (2020) and 5032.02 (2020).
• Although 773 tracts remained with the same geographic ID, a portion of tracts had their boundaries adjusted. A total of 594 tracts remained with the same land area (±1%) as they had in 2010. Land areas in 26 tracts increased or decreased by at least 10%.
• Stamford and Danbury were the two municipalities most affected by updated tract boundaries, with 8 tracts split in Stamford (resulting in 16 new tract IDs) and 5 in Danbury (resulting in 10 new tract IDs).
• Census tract 4256 (2010) in Litchfield County, previously shared between Norfolk and Canaan, is now divided into 4256.01 (2020, matching Norfolk's boundaries), and 4256.02 (2020, matching Canaan's).

How is my town affected?

Use the interactive map below to see how census tract boundaries changed between 2010 and 2020 censuses. Jump to 1 of 169 towns using the search tool in the lower-left corner. To zoom in and out, use "+" and "-" buttons.

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How did census tracts change in Hartford?

Hartford received one new census tract, from 40 in 2010 up to 41 in 2020.

Hartford, CT. Photo by Balazs Busznyak

• Hartford's census tract 5031 (2010), located in the Asylum Hill neighborhood, was divided into two new tracts: 5031.1 to the south of Farmington Avenue, and 5032.2 to the north.
• Census tract 5007 (2010) in the northeast corner of Hartford was replaced with an identically shaped tract 9801 (2020).
• A boundary between census tracts 5039 (2010, 2020) and 5040 (2010, 2020) was redrawn, increasing the size of tract 5040.

New Haven, CT. Photo by Joey Genovese

What changed for New Haven?

Like Hartford, New Haven now has a new census tract. The 2020 boundaries divvied the city into 32 tracts, compared to 31 in 2010.

• Census tract 1401 (2010) in downtown New Haven was split into 1401.01 to the west of Church Street, and 1401.02 to the east.
• The boundary between tracts 1413 (2010) and 1414 (2010) in the northwest corner of New Haven changed, resulting in the rename of tract 1413 (2010) to 1413.01 (2020).
• Census tract 1426.03 (2010) was renamed to 1426.05 (2020), although its boundaries did not shift substantially.
• The triangle formed by Washington, Howard, and Columbus Avenues was removed from tract 1403 (2010) and reassigned to tract 1406 (2020).

How did the updates affect Stamford?

Stamford, CT. Photo by Jose Ambelis

As one of the most dynamic cities in Connecticut, Stamford saw the most changes in census tract boundaries. The city now has 33 census tracts, compared to 25 in 2010.

• Census tract 201 (2010) in downtown Stamford was divided along Broad Street, resulting in two new tracts: 201.01 (2020) to the north, and 201.02 (2020) to the south.
• Census tract 203 (2010) in the north of the city was split into 203.01, east of Rock Rimmond Road, and 203.02 to the west.
• Census tract 214 (2010) was seperated into 2014.01 (2020) to the east of West Avenue, and 214.02 (2020) to the west.
• Census tract 215 (2010) was divided into 215.01 (2020) and 215.02 (2020) along West Main Street.
• Census tract 216 (2010) in the Northfield neighborhood was split into 216.01 (2020) west and 216.02 (2020) east of Bedford Street.
• Similarly, another downtown tract 217 (2010) was divided into 217.01 (2020) and 217.02 (2020); census tract 221 (2010) was split into 221.01 (2020) and 221.02 (2020) along Jefferson Street and Cove Road; census tract 222 (2010) was split into 222.01 (2020) and 222.02 (2020).

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Summary of 2020 Census Tracts Changes by Town

The list below summarizes changes in census tracts by municipality. Note that census tracts are not subdivisions of towns, and a tract may sometimes cross town boundaries. For example, according to 2010 boundaries, Norfolk and Canaan shared a large tract 4256 (although in 2020, the tract was split along town boundaries).

Most (not all) of the new tracts appeared due to splitting the old (2010) overcrowded tracts into two. For example, in Berlin, the old tract 4001 (marked as 4001 in the list) was split into tracts 4001.01 and 4001.02. Sometimes two tracts become one, as was the case with New Milford, where tracts 2533 and 2536 merged into a single tract 4257.

Even though your town may not be listed below, its tract boundaries may have changed without the tract being renamed. Use the interactive map above to learn more about the adjustments.

Berlin
4001 4001.01, 4001.02

Branford
1841 1841.01

Bristol
4058 4058.01, 4058.02

Brooklyn
9051 9051.01, 9051.02

Canaan
4256.02

Danbury
2101 2101.01, 2101.02, 2102 2102.01, 2102.02, 2104 2104.01, 2104.02, 2105 2105.01, 2105.02, 2112 2112.01, 2112.02

East Granby
9800.01

East Haven
1801 1801.01, 1801.02

Ellington
5351 5351.01, 5351.02

Essex
6301 6301.01, 6301.02

Haddam
5901 5901.01, 5901.02

Hamden
1660.01 1660.03, 1660.04

Hartford
5007 9801, 5031 5031.01, 5031.02

Killingly
9041 9041.01, 9041.02

Manchester
5141.02 5141.04, 5141.03

Meriden:
1712 1712.01, 1712.02

Middletown
5413 5413.01, 5413.02

New Canaan
351 351.01, 351.02

New Haven
1401 1401.01, 1401.02, 1413 1413.01, 1426.03 1426.05

New Milford
2533 2536 4257

Norfolk:
4256.01

North Haven
1671 1671.01, 1671.02, 1673 1673.01

Norwich
6964 6964.01, 6967 6967.01

Old Lyme
6601.02 6601.03, 6601.04

Plainville
4206 4206.01, 4206.02

Putnam
9031 9031.01, 9031.02

Rocky Hill
4903.02 4903.03, 4903.04

Seymour
1302 1302.01, 1302.02

Shelton
1106 1106.01, 1106.02

Southington
4305 4305.01, 4305.02, 4306.01 4306.03, 4306.04

Stafford
8902.04

Stamford
201 201.01, 201.02, 203 203.01, 203.02, 214 214.01, 214.02, 215 215.01, 215.02, 216 216.01, 216.02, 217 217.01, 217.02, 221 221.01, 221.02, 222 222.01, 222.02

Suffield
4771.02 4771.03, 4771.04, 9800.03

Tolland
5331.01 5331.03, 5331.04

Union
8902.03

Wallingford
1755 1755.01, 1755.02

Waterbury
3501 3501.01

West Haven
1541 1541.01, 1541.02

Westbrook
6801 6801.01, 6801.02

Westport
503 503.01, 503.02

Winchester
3201 3201.01, 3201.02

Windham
8005 8005.01, 8005.02

Windsor Locks
9800.02

Woodstock
9011 9011.01, 9011.02

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