A Gazetteer for the United States and Canada
Census Data for Onawa ...
The most recent Census Estimate<1> was for 2018 and it gave Onawa a population of 2,787 people.
The last Decennial Census<2> was in 2010, which gave Onawa a population of 2,998 people.
The city of Onawa is located in Monona County. The 2010 Census gave Monona County a population of 9,243 people. This means that Onawa had 32.44% of the county's total population, making it Monona's most populous community.
When the Census Bureau conducts a census for a city like Onawa, they draw a boundary around the area in which they are going to conduct their count - this defines the sampling area (usually shaped as 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 the population, area and housing for Onawa reflect the sampling area. Since the shape of the sampling area and the actual boundaries of Onawa might be different, it's best to check with the U.S. Census Bureau to resolve any difference between the two.
The 2010 Census shows that the sampling area for Onawa has a total area of 5.19 square miles [13.4 km²].
Monona County has a land area of 694 square miles [1,797.6 km²]. At 5.19 square miles [13.4 km²], Onawa has 0.75% of the county's total land area.
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° 1' 36" (or 42.03°) [Map]
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).
Population Density ...
Using the population (2,998 people) and land area (5.19 square miles [13.4 km²]) values from the 2010 Census, Onawa had a population density of 577 people per square mile [223.1 people/km²].
In comparison, the 2000 Census shows Onawa had a population of 3,091 people and a land area of 4.91 square miles [12.7 km²]. This gives a population density of 629 people per square mile [242.9 people/km²]
NOTE: Be aware that when comparing population density between the 2000 and the 2010 Census, there were changes in the sampling area for Onawa. You need to be careful when making such a comparison, the differences are likely to lead to an apple-to-oranges comparison. More information about these differences can be found in the section Census-to-Census Observations ... (see below).
Housing Units ...
At the time of the 2010 Census, Onawa had 1,519 Housing Units<3> and with its population of 2,998 people, this averages 1.97 people per Housing Unit.
The 2010 Census shows Onawa had a land area of 5.19 square miles [13.4 km²]. This translates to 292.8 Housing Units per square mile [113 housing units/km²].
From the Census of 2000: Onawa had 1,452 Housing Units, a population of 3,091 people and a land area of 4.91 square miles [12.7 km²]. This gives a density of 2.13 people per Housing Unit and 295.5 Housing Units per square mile [114.1 housing units/km²].
NOTE: Repeating the caution above (under Population Density), be aware that when comparing Housing Units between the 2000 Census and the 2010 Census, there were changes in the sampling area for Onawa and you need to be careful when comparing numbers between the censuses. More information about the changes can be found in the section called Census-to-Census Observations ... (see below).
Monona County ...
The county had a population of 9,243 people at the 2010 Census. With it's population of 2,998 people, Onawa represented 32.44% of the county's total.
In addition, where the city of Onawa has a population density of 577 people per square mile [223.1 people/km²], Monona County averages 13.32 people per square mile [5.14 people/km²].
For more information, please visit our Census Page for Monona County.
Population Rings for Onawa ...
To help identify the number of people who live in Onawa and the surrounding area, we have drawn concentric rings centered on Onawa. We counted the number of communities within each ring and summed their populations.<4>
Census-to-Census Observations ...
When the Census Bureau takes a census count (or enumeration) for Onawa, 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 Onawa. It's important to note that from one Census to the next, the shape and location of the polygon can change. If you need precision or details about the methodology of the Census, you should visit the U.S. Census Bureau for a definitive answer.
The sampling area (or polygon) given for the 2010 Census is 5.6% larger than the 2000 Census.
The 2010 Census shows that the total area for Onawa was 5.19 square miles [13.4 km²]. Of this total, only a minor amount of the area is covered by water.
The 2000 Census shows a total area of 4.91 square miles [12.7 km²]. Of this total, only a minor amount of the area is covered by water.
While generally coinciding with the GPS location (latitude/longitude) of Onawa, the latitude and longitude given by the Census Bureau actually indicates the GPS location of the polygon for Onawa.
For the 2010 Census, the location was given as:
Lat: 42.026758° (or 42°1'36" N) [Map]
For the 2000 Census, the location given was:
Lat: 42.027490° (or 42°1'38" N) [Map]
The difference indicates that the U.S. Census Bureau moved the location of the polygon for the 2010 Census 1,648 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 (#468464) to Onawa. This identifier also marks a GSP point on the map, and that point lies within the boundaries of Onawa. The GNIS point has been mapped to the latitude/longitude:
Lat: 42.027488° (or 42°1'38" N) [Map]
The GSP location given for the 2010 Census lies 641 feet to the southwest<6> of the point given by the GNIS for Onawa. For more information about this and the relationship of the various Federal Codes, please visit our Misc Page for Onawa.
Miscellaneous Information for Onawa ...
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 Monona County or the city of Onawa:
The GNIS Codes ...
The current system of identification is called the Geographic Names Information System (GNIS). The following GNIS codes relate to Onawa:
GNIS ID for Onawa: 468464
The FIPS Codes ...
An earlier (and largely obsolete) identification method was called the Federal Information Processing Standard (FIPS):
State Code: 19 (Iowa)
County Code: 133 (Monona County)
Place Code: 59115 (Onawa)
Misc. Census Codes ...
Onawa is located in Census Region #2 (the Midwest Region) and Division #4 (the West North-Central 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 city like Onawa, it does identify addresses that are in (or near) Onawa. 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 Onawa: 51040<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 Onawa.
Other Roadside Stops ...
Off-the-Road Links ...
The official website of the U.S. Census Bureau
Unfortunately, we don't know of a website for Onawa. If you can help, please contact us through our Feedback Page.
The official website for State of Iowa: https://www.iowa.gov/
The official website of the U.S. Board on Geographic Names (BGN)
The official website of the U.S. Geological Survey (USGS)
Please keep in mind that we can not guarantee the accuracy or timeliness of the information on this website, so use with care. We encourage you to double-check the information that is critical to you.
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This page was last modified: 27 Aug 2019