A Gazetteer for the United States and Canada
Census Data for Ottumwa ...
The most recent Census Estimate<1> was for 2018 and it gave Ottumwa a population of 24,550 people.
The last Decennial Census<2> was in 2010, which gave Ottumwa a population of 25,023 people.
The city of Ottumwa is located in Wapello County. The 2010 Census gave Wapello County a population of 35,625 people. This means that Ottumwa had 70.2% of the county's total population, making it Wapello's most populous community.
When the Census Bureau conducts a census for a city like Ottumwa, 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 Ottumwa reflect the sampling area. Since the shape of the sampling area and the actual boundaries of Ottumwa 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 Ottumwa has a total area of 16.53 square miles [42.8 km²]. Of this total, 15.86 square miles [41.1 km²] is land, with the balance (4.07%) being water (0.67 square miles [1.7 km²]).
Wapello County has a land area of 431.8 square miles [1,118.4 km²]. At 15.86 square miles [41.1 km²], Ottumwa has 3.67% 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: 41° 1' 20" (or 41.02°) [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 (25,023 people) and land area (15.86 square miles [41.1 km²]) values from the 2010 Census, Ottumwa had a population density of 1,513 people per square mile [584 people/km²].
In comparison, the 2000 Census shows Ottumwa had a population of 24,998 people and a land area of 15.8 square miles [40.9 km²]. This gives a population density of 1,517 people per square mile [585 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 Ottumwa. You need to be careful when making such a comparison, the differences are likely to lead to a misleading comparison. More information about the nature of these differences can be found in the section Census-to-Census Observations ... (see below).
Housing Units ...
At the time of the 2010 Census, Ottumwa had 11,257 Housing Units<3> and with its population of 25,023 people, this averages 2.22 people per Housing Unit.
The 2010 Census shows Ottumwa had a land area of 15.86 square miles [41.1 km²]. This translates to 681 Housing Units per square mile [262.9 housing units/km²].
From the Census of 2000: Ottumwa had 11,038 Housing Units, a population of 24,998 people and a land area of 15.8 square miles [40.9 km²]. This gives a density of 2.26 people per Housing Unit and 670 Housing Units per square mile [258.7 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 Ottumwa and you need to be careful when comparing values between the censuses. More information about these differences can be found in the section called Census-to-Census Observations ... (see below).
Wapello County ...
The county had a population of 35,625 people at the 2010 Census. With it's population of 25,023 people, Ottumwa represented 70.2% of the county's total.
In addition, where the city of Ottumwa has a population density of 1,513 people per square mile [584 people/km²], Wapello County averages 82.5 people per square mile [31.85 people/km²].
For more information, please visit our Census Page for Wapello County.
Population Rings for Ottumwa ...
To help identify the number of people who live in Ottumwa and the surrounding area, we have drawn concentric rings centered on Ottumwa. 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 Ottumwa, 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 Ottumwa. 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.
There is only a very minor difference in the sampling area given between the 2010 Census and the 2000 Census.
The 2010 Census shows that the total area for Ottumwa was 16.53 square miles [42.8 km²]. Of this total, 15.86 square miles [41.1 km²] is land, with the balance (4.07%) being water (0.67 square miles [1.7 km²]).
The 2000 Census shows a total area of 16.47 square miles [42.7 km²]. Of this total, 15.8 square miles [40.9 km²] is land, with the balance (4.08%) being water (0.67 square miles [1.7 km²]).
While generally coinciding with the GPS location (latitude/longitude) of Ottumwa, the latitude and longitude given by the Census Bureau actually indicates the GPS location of the polygon for Ottumwa.
For the 2010 Census, the location was given as:
Lat: 41.022337° (or 41°1'20" N) [Map]
For the 2000 Census, the location given was:
Lat: 41.012917° (or 41°0'46" N) [Map]
The difference indicates that the U.S. Census Bureau moved the location of the polygon for the 2010 Census 4,167 feet to the northwest<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 (#2396110) to Ottumwa. This identifier also marks a GSP point on the map, and that point lies within the boundaries of Ottumwa. The GNIS point has been mapped to the latitude/longitude:
Lat: 41.019526° (or 41°1'10" N) [Map]
The GSP location given for the 2010 Census lies 1,635 feet to the northwest<6> of the point given by the GNIS for Ottumwa. For more information about this and the relationship of the various Federal Codes, please visit our Misc Page for Ottumwa.
Miscellaneous Information for Ottumwa ...
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 Wapello County or the city of Ottumwa:
The GNIS Codes ...
The current system of identification is called the Geographic Names Information System (GNIS). The following GNIS codes relate to Ottumwa:
GNIS ID for Ottumwa: 2396110
The FIPS Codes ...
An earlier (and largely obsolete) identification method was called the Federal Information Processing Standard (FIPS):
State Code: 19 (Iowa)
County Code: 179 (Wapello County)
Place Code: 60465 (Ottumwa)
Misc. Census Codes ...
Ottumwa 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 Ottumwa, it does identify addresses that are in (or near) Ottumwa. 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 Ottumwa: 52501<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 Ottumwa.
Other Roadside Stops ...
Off-the-Road Links ...
The official website of the U.S. Census Bureau
The official website for Ottumwa: www.ci.ottumwa.ia.us/
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)
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This page was last modified: 27 Aug 2019