Iowa is the U.S. state with the most factory farms: 10,830 of them, to be exact. The massive scale of animal agriculture in Iowa produces staggering amounts of manure, more than its fields of corn, soy and other crops can absorb.
This has a devastating effect on the state’s water. When too much manure is spread on fields, nitrates run off into the groundwater and nearby streams and lakes.
Small towns in Iowa can face months-long stretches when their water is undrinkable. Des Moines, the state capitol and largest city, operates a massive system to remove nitrate pollution from its water to the tune of $10,000 a day, the largest such system in the world when it was built. More than half of Iowa’s rivers and streams, and more than 60% of its lakes and reservoirs, failed water quality standards in 2024.
This water crisis is linked to an unfolding public health threat.
Iowa has the fastest-growing cancer rate in the nation, and drinking water high in nitrates is linked to a higher risk of colorectal, kidney, thyroid, prostate and breast cancer. Iowa’s rates of all of these cancers are higher than the national average.
Though nitrate pollution and its link to cancer risk is perhaps most evident in Iowa, similar dynamics are at play in agricultural states all over the country, such as North Carolina, Minnesota and Georgia, which each have thousands of large livestock farms generating manure. Almost 20% of Americans have high levels of nitrates in their drinking water, according to an Environmental Working Group analysis.
What’s happening in Iowa right now, in addition to affecting its more than 3.2 million residents, may be a warning flare for crises brewing in other states.
However, there’s no easy way for Iowans to find out how much manure industrial farms are producing or exactly where in the state it’s coming from. Even the state Department of Natural Resources doesn’t collect records of where companies apply their manure, because these are legally confidential in Iowa. The agency does collect farms’ plans for manure management, but not whether they are followed, and there is no user-friendly public database where Iowans can easily find the manure plans or the information they contain.
So Sentient Media set out to make information about Iowa’s manure as accessible as possible. This meant mapping every factory farm in Iowa and estimating their manure output using state data and federal animal waste research.
We built an interactive map that allows Iowans to find factory farms in their own backyards — and readers across the country to see what’s happening in one of the states where much of their bacon and eggs come from. Readers can use the map to see an estimate of how much manure factory farms are producing in a city, county or ZIP code or within a certain radius of any address, as well as view any nearby waterways or floodplains.
While the records of exactly where a farm spreads its manure are still confidential in Iowa, knowing where the manure is produced is informative. In Iowa, liquid manure is spread an average of two miles from where it is produced and solid manure an average of 14.5 miles, according to a survey of manure applicators by Iowa State University researchers.
Here are some of the most striking insights found from analyzing Iowa’s nearly 11,000 factory farms, home to 126.4 million animals, and their estimated annual manure output, violations and more.
All findings are based on Iowa Department of Natural Resources data and Sentient Media manure estimates (our methodology is here). Sentient Media has made the data and underlying code behind the map available on GitHub.
#1. Livestock on Iowa factory farms produce nearly 170 billion pounds of manure each year.
Sentient Media estimates that Iowa’s Concentrated Animal Feeding Operations, or CAFOs, produce about 170 billion pounds of manure per year.
The estimation includes all livestock operations in the state that house 300 or more animal units. Although facilities that house between 300 and 500 animal units are not required by the state of Iowa to provide manure management plans, they are included in the EPA’s definition of Concentrated Animal Feeding Operations.
Hogs in Iowa produce the most waste, with an estimated 100 billion pounds per year. Iowa is the top pork-producing state in the country, home to 25 million pigs with an estimated $40 billion in annual sales, according to industry statistics. The state raises one in every three hogs in the country.
After hogs, beef cattle in Iowa produce the most manure: 44 billion pounds annually. The nation’s beef cattle herd is currently at a 75-year low, and Iowa’s beef herd, as part of that, is down slightly in numbers. Iowa’s $6.19 billion beef industry may also be impacted by the recent closures of major beef processing facilities, such as the Tyson plant in Joslin, Illinois.
#2. Despite being known for its hogs, most of the state’s top 10 manure producers are dairy operations.
Iowa is known for its hogs, but of the top ten facilities that produce the most manure, none are hog farms. Five are dairy farms, three raise beef cattle and two contain egg-laying hens.
A single dairy confinement in northwest Iowa alone produces nearly a billion pounds of manure each year. This is City View Farms of Sutherland, Iowa, the Iowa CAFO that produces the most manure in the state. City View Farms confines about 24,000 dairy cattle. Dairy cattle often produce over 100 pounds of manure per day, making large dairy CAFOs intensive manure producers.
#3. Rural Iowa towns are packed with factory farms.
Iowa hosts a whopping 10,830 factory farms. That’s five times as many as the state’s gas stations, and eight times as many as the state’s grocery stores or public school buildings.
This means that many Iowa towns are full of CAFOs. Some have over 150 within their town limits.
These 10 towns in Iowa, ranging in population from about 750 to about 10,000, have the highest concentration of factory farms. Hog farms dominate in almost all of them.
For example, Rock Valley, in the northwest corner of the state, has a human population of only 4,059, but its 152 factory farms house 617,222 animals, outnumbering people by roughly 150 to 1. The town of Alden in north central Iowa has a population of 763, but contains 93 factory farms housing 419,000 animals.
#4. Counties in northwest Iowa are packed with manure.
The northwest corner of Iowa is particularly dense with factory farms. Sioux County, Iowa, home to about 37,000 people over 768 square miles, produces an estimated 20 billion pounds of manure within its borders each year, about one-eighth of the total for the entire state.
To see manure totals for any county, viewers can select their county by clicking on the map or searching for a county in the dropdown menu.
#5. Iowa’s Department of Natural Resources issued more violation notices last year.
The Iowa Department of Natural Resources is responsible for issuing citations for operations that spill manure into waterways or mishandle their waste. The agency has worked with minimal staff and a stagnant budget in recent years, leading to criticism for its lack of enforcement efforts. The agency employs roughly a thousand employees, though only a small portion of those oversee waste from factory farms. Agency officials are hugely outnumbered by the number of operations they are responsible for monitoring.
Sentient Media’s interactive map pulls violation notice records from the agency’s website going back to 2003. By clicking on a specific CAFO, you can see its compliance dashboard, featuring any violation notices during that time as well as a link to the Iowa Department of Natural Resources’ compliance portal for that specific operation.
Based on this data, the agency issued 522 violation notices in 2025, more than any year in the previous decade and up nearly a third from 2024. However, not all of those violations may have been for manure pollution. A previous analysis by Sentient and Inside Climate News of fines issued by the agency from January 1, 2020 to December 31, 2025 found that most fines were for administrative violations such as late plans, rather than for manure spills, application of too much manure, or other possible pollution events.
Out of the nearly 11,000 CAFOs on the new interactive map, 45% have had one or more violation since 2003.
Sentient Media reached out to the Iowa Department of Natural Resources and did not receive comment.
The operation with the most notices of violation in the state is Daybreak Foods, Inc., an egg production and processing facility in Eagle Grove, Iowa. The facility is home to roughly 6 million egg-laying hens and has received at least over 30 notices from the Department of Natural Resources since 2003.
Daybreak Foods supplies eggs to McDonald’s and operates egg facilities in Iowa, Wisconsin, Minnesota and Ohio.
Another notable facility with notices of violation is a beef feedlot in Monona, Iowa called Supreme Beef. For years, the community group Driftless Water Defenders has been fighting this facility, claiming that its waste pollutes local protected trout stream Bloody Run Creek and bringing a lawsuit against the Department of Natural Resources. The 10,000-head feedlot has a dozen notices of violation on record since 2017.
The issue of clean water has been gathering force in Iowa for years and may have consequences far beyond the borders of the state. A majority of Iowans across party lines have expressed that clean water is a driving force in their voting during a consequential year in Iowa politics. While the state still keeps official records of where manure is spread confidential from the public, Iowans can now see in detail how much manure is produced and where, arming them with information to better understand the compounding water and cancer crises that affect their daily lives.
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