[2] The county was named by Joshua D. Brown for his fellow Kentucky native, James Kerr, a congressman of the Republic of Texas.

Around 8000 BC, early Native American inhabitants arrived in the area, with numerous successive cultures following in prehistoric times.

Historic tribes encountered by Europeans included the Kiowa, Comanche, and Lipan Apache.

[3] In 1842, the Adelsverein[4] Fisher–Miller Land Grant set aside 3,000,000 acres (1,200,000 ha) to settle 600 families and single men of German, Dutch, Swiss, Danish, Swedish, and Norwegian ancestry in Texas.

In 1845, Prince Carl of Solms-Braunfels secured the title to 1,265 acres (512 ha) of the Veramendi grant, including the Comal Springs and River, for the Adelsverein.

Thousands of German immigrants were stranded at port of disembarkation, Indianaola on Matagorda Bay.

With no food or shelter, living in holes dug into the ground, an estimated 50% died from disease or starvation.

[3] The U.S. Camel Corps, headquartered at Verde, was the brainchild of United States Secretary of War (1853–57) Jefferson Davis.

Unionists from Kerr, Gillespie, and Kendall Counties participated in the formation of the Union League, an organization which supported President Lincoln's policies.

[13] The Union League formed companies to protect the frontier against Indians and their families against local Confederate forces.

Spring Creek Cemetery near Harper in Gillespie County has a singular grave with the names Sebird Henderson, Hiram Nelson, Gus Tegener, and Frank Scott.

It is the only monument to the Union outside of the National Cemeteries on Confederate territory, and is one of only six such sites allowed to fly the United States flag at half-mast in perpetuity.

The American Legion of Texas established what eventually was called the Veterans Affairs Medical Center, Kerrville, in 1919.