Marietta, IndianaMarietta is an unincorporated community in Hendricks Township, Shelby County, in the U.S. state of Indiana.HistoryMarietta was platted in 1839. A post office was established at Marietta in 1848, and remained in operation until it was discontinued in 1904. Marietta once contained a high school which was discontinued at an unknown date.DemographicsThe United States Census Bureau defined Marietta as a census designated place in the 2022 American Community Survey.