Delaware County is a county located in the U.S. state of Oklahoma. As of the 2010 census, the population was 41,487. Its county seat is Jay. The county was named for the Delaware Indians who had established a village in the area prior to the arrival of the Cherokees in 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.