There are 23 US Post Offices in Iroquois County serving a total of 28,182 residents equating to 1,225 residents per post office. It's estimated that approximately 44,982 packages are handled across the 23 county post offices annually. Iroquois County is a county located in the northeast part of the U.S. state of Illinois. According to the 2010 census, it has a population of 29,718. It is the only county in the United States to be named Iroquois, after the American Indian people. The county seat is Watseka. The county is located along the border with Indiana."