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Census Data for Chelmsford

Population ...

The most recent Census Estimate<1> was for 2019 and it gave Chelmsford a population of 35,391 people.

The last Decennial Census<2> was in 2010, which gave Chelmsford a population of 33,802 people.

The community of Chelmsford is located in Middlesex County. The 2010 Census gave Middlesex County; a population of 1,503,085 people. This means that Chelmsford had 2.25% of the county's total population, making it Middlesex's 14th most populous community.

At the same time, Massachusetts had a population of 6,547,629 people, meaning that Chelmsford had 0.52% of the total population of Massachusetts - making it the state's 47th most populous community.

Area ...

The 2010 Census shows that the sampling area for Chelmsford has a total area of 23.08 square miles [59.8 km²]. Of this total, 22.37 square miles [57.9 km²] is land, with the balance (3.09%) being water (0.71 square miles [1.8 km²]).

Middlesex County has a land area of 817 square miles [2,118.1 km²]. At 22.37 square miles [57.9 km²], Chelmsford has 2.74% of the county's total land area.

  • Continue Reading ...
    • When the Census Bureau conducts a census for a community like Chelmsford, they draw a boundary around the area in which they are going to conduct their count - this defines the sampling area (usually a polygon). The shape of the sampling area can be quite complex and it's important to keep in mind that the boundaries of the sampling area may or may not match the recognized boundaries of the community.
    • Things like population, area and housing for Chelmsford reflect the sampling area. Since the shape of the sampling area and the actual boundaries of Chelmsford might be different, it's best to check with the U.S. Census Bureau to resolve any difference between the two.
    • Not only does the sampling area define boundaries, it also has a GPS location (latitude & longitude) that indicates a point within the sampling area (usually the center of the polygon, known as the centroid). At the time of the 2010 Census, the sampling area was located at:
    • Lat:   42° 35' 49"   (or 42.6°)
    • Lon:   -71° 22' 11"   (or -71.37°)
    • More information on this topic and the changes between the 2000 Census and the 2010 Census can be found in the section for our Census-to-Census Observations ... (see below).

Housing Units ...

At the time of the 2010 Census, Chelmsford had 13,807 Housing Units<3> and with its population of 33,802 people, this averages 2.45 people per Housing Unit.

  • Continue Reading ...
    • The 2010 Census shows Chelmsford had a land area of 22.37 square miles [57.9 km²]. This translates to 598 Housing Units per square mile [230.9 housing units/km²].
    • From the Census of 2000: Chelmsford had 13,025 Housing Units, a population of 33,858 people and a land area of 22.65 square miles [58.7 km²]. This gives a density of 2.6 people per Housing Unit and 561 Housing Units per square mile [217 housing units/km²].
    • Note: Repeating the caution above (under Population Density), be aware that when comparing Housing Units between the 2010 and the 2000 Census, there were changes in the sampling area for Chelmsford and you need to be careful when comparing numbers between the censuses. More information about the nature of these the changes can be found in the section called Census-to-Census Observations ... (see below).

Middlesex County ...

Chelmsford is located in Middlesex County<4>.

The county had a population of 1,503,085 people at the 2010 Census. With it's population of 33,802 people, Chelmsford represented 2.25% of the county's total.

In addition, where the community of Chelmsford has a population density of 1,464 people per square mile [565 people/km²], Middlesex County averages 1,837 people per square mile [709 people/km²].

For more information, please visit our Census Page for Middlesex County.

Census-to-Census Observations ...

Introduction ...

When the Census Bureau takes a census count (or enumeration) for Chelmsford, they start by specifying the boundaries of the area to be counted. This area (or sampling area) is a polygon and its shape can be quite complex - it may or may not match the geographical boundaries of Chelmsford. It's important to note that from one Census to the next, the shape and location of the polygon can change.

  • Continue Reading ...
    • Although we don't have specific information about the shape of the polygon for Chelmsford or how it changed has over time, there is some information that can give us some hints. For example, since the shape of the sampling area is directly related to the shape of the polygon, any change to area probably indicates a new shape for the polygon.
    • If you need precision or details about the methodology of the Census, you should visit the U.S. Census Bureau for a definitive answer.

Location ...

While generally coinciding with the GPS location (latitude/longitude) of Chelmsford, the latitude and longitude given by the Census Bureau actually indicates the GPS location of the polygon for Chelmsford.

  • Continue Reading ...
    • For the 2010 Census, the location was given as:
    • Lat:   42.597001°   (or 42°35'49" N)
    • Lon:   -71.369759°   (or -71°22'11" W)
    • For the 2000 Census, the location given was:
    • Lat:   42.603824°   (or 42°36'13" N)
    • Lon:   -71.365181°   (or -71°21'54" W)
    • The difference indicates that the U.S. Census Bureau moved the location of the polygon for the 2010 Census 2,774 feet to the southwest<5> of the location that was used in the 2000 Census.
    • The U.S. Geological Survey (USGS) and the U.S. Board on Geographic Names (BGN) have assigned a unique GNIS identifier (#618220) to Chelmsford. This identifier also marks a GPS point on the map, and that point lies within the boundaries of Chelmsford. The GNIS point has been mapped to the latitude/longitude:
    • Lat:   42.599814°   (or 42°35'59" N)
    • Lon:   -71.367284°   (or -71°22'2" W)
    • The GPS location given for the 2010 Census lies 1,221 feet to the southwest<6> of the point given by the GNIS for Chelmsford. For more information about this and the relationship of the various Federal Codes, please visit our Misc Page for Chelmsford.

Miscellaneous Information for Chelmsford ...

The Federal government has assigned various identifying codes to each community, county and state. At one time or another, the US Census Bureau has used one (or more) of the following identifiers when referring to either Middlesex County or the community of Chelmsford:

  • The GNIS Codes ...
    • The current system of identification is called the Geographic Names Information System (GNIS). The following GNIS codes relate to Chelmsford:
    • GNIS ID for Chelmsford: 618220
    • GNIS ID for Middlesex County: 606935
    • GNIS ID for State of Massachusetts: 606926
  • Misc. Census Codes ...
    • Chelmsford is located in Census Region #1 (the Northeast Region) and Division #1 (the New England Division).
  • The US Postal Service ZIP Code ...
    • While some people have used a ZIP code to identify a community, the purpose of the ZIP code was to make mail delivery more efficient by grouping addresses together. Although the ZIP Code doesn't specifically identify a community like Chelmsford, it does identify addresses that are in (or near) Chelmsford. It's important to remember that the boundaries of a ZIP Code can be changed, re-assigned or overlapped with other ZIP Codes.
    • The ZIP code for Chelmsford:01824<7>
  • Census ZCTA Codes ...
    • The US Census Bureau created statistical entities that they call ZIP Code Tabulation Areas (ZCTAs) and these ZCTAs are frequently confused with the ZIP codes that come from the US Postal Service (USPS).
    • ZCTAs were first created for the 2000 Census and at that time, they were based upon the USPS ZIP codes. While largely covering the same areas, the boundaries of a ZCTA do not necessarily match the boundaries of a postal ZIP code with the same number. For example, while a postal ZIP code can cross a county or state line, a Census ZCTA can not. They should be treated as separate entities with no correlation between them.

For more information about the various Federal identification codes, please visit our Misc Page for Chelmsford.

Unfortunately, we don't know of a website for Chelmsford. If you can help, please contact us through our Feedback Page.

The official website for State of Massachusetts:

The official website of the U.S. Census Bureau

The official website of the U.S. Board on Geographic Names (BGN)

The official website of the U.S. Geological Survey (USGS)

Footnotes ...

<1>Every year, the US Census Bureau creates a population estimate for the preceeding year. Keep in mind that this value is an estimate and not an actual count. The most recent Census estimate is for the year 2019.
<2>Every 10 years (eg- 1990, 2000, 2010), the US Census Bureau conducts a Constitutionally-mandated count (or enumeration) of people living within the United States. This count is called a Decennial Census. The last Decennial Census was the 2010 Census, with the next one planned for 2020.
<3>A Housing Unit is a broad term for those places where people live (whether occupied or temporarily vacant), such as a house, an apartment, a mobile home, or an area that is considered as a separate living quarter. Separate living quarters (consisting of one or more rooms) are considered to be those places where people live, sleep and eat separately from others and that have access to the outside (either directly or by a shared hallway).
<4>If you're interested in how the shape of Massachusetts' counties, including Middlesex, have changed over time, we recommend the Atlas of Historical County Boundaries.
<5>The calculated bearing (or angle) to the 2010 Census location is 153 degrees and a distance of 2,774 feet.
<6>The calculated bearing (or angle) to the GNIS point is 147 degrees and a distance of 1,221 feet.
<7>When looking for a ZIP Code, whether Chelmsford or elsewhere, it's always best to check the website of the United States Postal Service (USPS).


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This page was last modified/updated: 07 Apr 2024