This mostly rural county has an overwhelmingly ethnic European-American population, which has declined in number since the early 20th century as people have moved to cities.
The borderlands of Kansas and Missouri were battlegrounds for insurgents during the American Civil War, with raids going back and forth across the border. Bates County is noted as the site for the first combat engagement during the war of African-American soldiers serving with the Union and against Confederate forces, which occurred on October 28–29, 1862. The First Kansas Colored Division (part of the state militia) fought Confederate guerrillas at the Battle of Island Mound four miles north of present-day Rich Hill, Missouri, and the Union forces won.
The Kansas soldiers were badly outnumbered but stood their ground, fighting valiantly. The skirmish was covered by The New York Times, which noted the men's bravery at a time when many people questioned whether former slaves could make good soldiers. Their heroic action preceded President Abraham Lincoln's announcement of the Emancipation Proclamation in January 1863 and establishment of the United States Colored Troops.
Following a massacre of men and boys and the burning of Lawrence, Kansas, by Confederate bushwhackers in the summer of 1863, the United States General Ewing ordered the evacuation of the civilian population from rural areas of Bates and nearby counties except for within a mile of certain Union-controlled cities, in order to cut off sources of support for Confederate insurgents. This was done under Order No. 11. The county had been a base of Confederate guerrillas. But, Ewing's order generated outrage and added to support of guerrillas in some areas.
This mostly rural county continued to support agriculture in the decades after the Civil War. Since the late 20th century, population has declined as people have moved to cities for work.
Legacy and honors
A statue commemorating the Battle of Island Mound was installed on the north lawn of the county courthouse in Butler, seven miles from the skirmish site.
The Battle of Island Mound (2014) is a short documentary film made in cooperation with the Missouri Department of Natural Resources; it won two Emmy Awards in 2015 for historic documentary and cinematography.
According to the U.S. Census Bureau, the county has a total area of 851 square miles (2,200 km2), of which 837 square miles (2,170 km2) is land and 15 square miles (39 km2) (1.7%) is water.
There were 6,511 households out of which 32.30% had children under the age of 18 living with them, 58.80% were married couples living together, 7.60% had a female householder with no husband present, and 30.00% were non-families. 26.10% of all households were made up of individuals and 13.90% had someone living alone who was 65 years of age or older. The average household size was 2.51 and the average family size was 3.02.
In the county, the population was spread out with 26.50% under the age of 18, 7.50% from 18 to 24, 26.00% from 25 to 44, 22.60% from 45 to 64, and 17.40% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 95.20 males. For every 100 females age 18 and over, there were 91.50 males.
The median income for a household in the county was $30,731, and the median income for a family was $36,470. Males had a median income of $30,298 versus $19,772 for females. The per capita income for the county was $15,477. About 11.50% of families and 14.50% of the population were below the poverty line, including 18.30% of those under age 18 and 14.10% of those age 65 or over.
Bates County has become increasingly Republican over the past few presidential elections. Since the 2000 election, the county has become more Republican with each election cycle. The last time a democratic candidate has carried this county was in 1996 by Bill Clinton.