Delta County is a county in the Upper Peninsula in the U.S. state of Michigan. As of the 2020 census, the population was 36,903. The county seat is Escanaba. The county was surveyed in 1843 and organized in 1861. Its name originates from the Greek letter delta, which refers to the triangular shape of the original county which included segments of Menominee, Dickinson, Iron, and Marquette counties.