The Iowa Cow War of 1931 involved violent disputes over the testing of cows for tuberculosis. After distrustful farmers tried and failed to repeal the testing program, they gathered in numbers to block tests from taking place. Such confrontations sometimes led to violence. Subsequently, the Republican Governor Dan Turner of Iowa declared martial law and called out Iowa National Guard troops to restore peace and to assist in capturing the ringleaders Jake Lenker and Paul Moore.
The State of Iowa required the tests to reduce the frequency with which dairy cattle with tuberculosis would contaminate the milk supply and cause milk-drinking humans to contract the disease.[1] An Iowa law passed in 1929 required all dairy and breeding cattle be tested by veterinarians. Any animal that showed signs of infection was to be destroyed. The owner was paid an indemnity. The program was financed by a property tax levy of up to 3 mills.[1]
The adoption of the testing program unfortunately coincided with the Great Depression. Farmers already impoverished by low prices for their milk and beef viewed the testing program as another threat to their livelihood.[1] They claimed that the test was unreliable and caused abortions in cattle. They also asserted that the test lowered the quality of milk and reduced a cow's milk output.[1]
In February 1931, two years after the adoption of the testing law, an estimated one thousand farmers went by special train from Tipton, Iowa (in Cedar County, Iowa) to Iowa's Capitol in Des Moines. On arrival, they demanded that Iowa Legislature make the tests optional rather than mandatory. After the Legislature refused to act, farmers began to take things into their own hands.[1]
In rural areas of southeast Iowa, veterinarians attempting to test cattle were increasingly met by large groups of farmers mobilized to obstruct the tests.[1] They were subjected to minor levels of violence, such as thrown eggs or mud, and kicks from farm wives.[1]
In areas where testing had been frustrated, Iowa officials responded by providing veterinarians with escorts from law officers. This came to a head on September 21, 1931 at the Jake Lenker farm south of Tipton.[2] Two veterinarians convoyed by 65 officers appeared at the farm. Barring the way were 400 farmers. Violence flared.[1] The following day, Iowa Governor Dan Turner declared martial law and sent 31 Iowa National Guard units to Tipton.[1] The effect of this show of force was dramatic. As Iowa historian George Mills explained decades later, "Objecting farmers gave in almost without exception to the show of force."[1] When all of the tests were completed (often under armed guard), the conflict also ended.[1]
Ultimately, Lenker and another leader of the revolt, Paul Moore, were arrested and convicted of criminal conspiracy, and sentenced to three-year terms in the Iowa State Pentitentiary in Fort Madison, Iowa.[1] Each was paroled well before the end of their sentences.