Census Data for Janesville
Population ...
The most recent Census Estimate<1> was for 2019 and it gave Janesville a population of 64,497 people.
The last Decennial Census<2> was in 2010, which gave Janesville a population of 63,575 people.
The city of Janesville is located in Rock County. The 2010 Census gave Rock County; a population of 160,260 people. This means that Janesville had 39.67% of the county's total population, making it Rock's most populous community.
At the same time, Wisconsin had a population of 5,686,986 people, meaning that Janesville had 1.12% of the total population of Wisconsin - making it the state's 10th most populous community.
Area ...
The 2010 Census shows that the sampling area for Janesville has a total area of 34.45 square miles [89.2 km²]. Of this total, 33.86 square miles [87.7 km²] is land, with the balance (1.71%) being water (0.59 square miles [1.5 km²]).
Rock County has a land area of 718 square miles [1,860 km²]. At 33.86 square miles [87.7 km²], Janesville has 4.71% of the county's total land area.
- Continue Reading ...
- When the Census Bureau conducts a census for a city like Janesville, 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 city.
- Things like population, area and housing for Janesville reflect the sampling area. Since the shape of the sampling area and the actual boundaries of Janesville 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° 41' 4" (or 42.68°)
- Lon: -89° 0' 47" (or -89.01°)
- 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, Janesville had 27,996 Housing Units<3> and with its population of 63,575 people, this averages 2.27 people per Housing Unit.
- Continue Reading ...
- The 2010 Census shows Janesville had a land area of 33.86 square miles [87.7 km²]. This translates to 812 Housing Units per square mile [313.8 housing units/km²].
- From the Census of 2000: Janesville had 25,083 Housing Units, a population of 59,498 people and a land area of 27.54 square miles [71.3 km²]. This gives a density of 2.37 people per Housing Unit and 891 Housing Units per square mile [344.4 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 Janesville and you need to be careful when comparing results 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).
Rock County ...
Janesville is located in Rock County<4> and is the County Seat for Rock County.
The county had a population of 160,260 people at the 2010 Census. With it's population of 63,575 people, Janesville represented 39.67% of the county's total.
In addition, where the city of Janesville has a population density of 1,845 people per square mile [712 people/km²], Rock County averages 223.2 people per square mile [86.2 people/km²].
For more information, please visit our Census Page for Rock County.
Census-to-Census Observations ...
Introduction ...
When the Census Bureau takes a census count (or enumeration) for Janesville, 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 Janesville. 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 Janesville 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 Janesville, the latitude and longitude given by the Census Bureau actually indicates the GPS location of the polygon for Janesville.
- Continue Reading ...
- For the 2010 Census, the location was given as:
- Lat: 42.684698° (or 42°41'4" N)
- Lon: -89.013170° (or -89°0'47" W)
- For the 2000 Census, the location given was:
- Lat: 42.684110° (or 42°41'2" N)
- Lon: -89.016654° (or -89°0'59" W)
- The difference indicates that the U.S. Census Bureau moved the location of the polygon for the 2010 Census 958 feet to the east<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 (#1583448) to Janesville. This identifier also marks a GPS point on the map, and that point lies within the boundaries of Janesville. The GNIS point has been mapped to the latitude/longitude:
- Lat: 42.684733° (or 42°41'5" N)
- Lon: -89.015667° (or -89°0'56" W)
- The GPS location given for the 2010 Census lies 669 feet to the east<6> of the point given by the GNIS for Janesville. For more information about this and the relationship of the various Federal Codes, please visit our Misc Page for Janesville.
Miscellaneous Information for Janesville ...
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 Rock County or the city of Janesville:
- The GNIS Codes ...
- The FIPS Codes ...
- An earlier (and largely obsolete) identification method was called the Federal Information Processing Standard (FIPS):
- State Code: 55 (Wisconsin)
- County Code: 105 (Rock County)
- Place Code: 37825 (Janesville)
- State & County Code: 55/105 (Wisconsin / Rock County)
- State & Place Code: 55/37825 (Wisconsin / Janesville)
- Misc. Census Codes ...
- Janesville is located in Census Region #2 (the Midwest Region) and Division #3 (the East North-Central Division).
For more information about the various Federal identification codes, please visit our Misc Page for Janesville.
Off-the-Road Links ...
The official website for Janesville: www.ci.janesville.wi.us/
The official website for Rock County: www.co.rock.wi.us/
The official website for State of Wisconsin: https://www.wisconsin.gov/
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 Wisconsin's counties, including Rock, have changed over time, we recommend the Atlas of Historical County Boundaries. |
| <5> | The calculated bearing (or angle) to the 2010 Census location is 282 degrees and a distance of 958 feet. |
| <6> | The calculated bearing (or angle) to the GNIS point is 268 degrees and a distance of 669 feet. |