Delaware County is a county located in the U.S. state of Oklahoma. As of the 2020 census, the population was 40,397. Its county seat is Jay. The county was named for the Delaware Indians, who had established a village in the area prior to the Cherokees being assigned to relocate to Indian Territory in the 1830s. Delaware County was created in 1907. Prior to becoming Delaware County, a large portion of the area was known as the Delaware District of the Cherokee Nation.