Rio is an unincorporated community and census-designated place (CDP) in Martin County, Florida, United States. The population was 980 at the 2020 census. Rio is pronounced locally as if it were spelled "Rye-oh". It is part of the Port St. Lucie Metropolitan Statistical Area. Government Rio sits in Martin County District 1, which includes parts of Stuart, Jensen Beach, Hutchinson Island, and Sewall's Point. History Rio proper was platted as "Rio St. Lucie", but the post office established on March 24, 1893, was called "Rio San Lucie". On December 1, 1897, the post office name was shortened to "Rio". The Rio post office was discontinued on March 15, 1902, with the area being taken over by the post office at Goslingville, which was located on the narrow peninsula just north of the present-day Roosevelt Bridge. On April 6, 1904, the Rio post office was reactivated and it continued until October 15, 1927, when it was added to the post office at Jensen, now known as Jensen Beach. Geography Rio is located in northeastern Martin County at (27.218419, -80.240037). It sits on the north side of the St. Lucie River across from Stuart, the county seat. It is bordered to the north and east by Jensen Beach and to the northwest by part of the Stuart city limits. According to the United States Census Bureau, the Rio CDP has a total area of , of which are land and , or 58.19%, are water. Demographics As of the census of 2000, there were 1,028 people, 495 households, and 283 families residing in the CDP. The population density was . There were 622 housing units at an average density of . The racial makeup of the CDP was 97.96% White, 0.49% African American, 0.10% Native American, 0.39% Asian, 0.10% Pacific Islander, 0.29% from other races, and 0.68% from two or more races. Hispanic or Latino of any race were 1.75% of the population. There were 495 households, out of which 18.4% had children under the age of 18 living with them, 44.4% were married couples living together, 7.9% had a female householder with no husband present, and 42.8% were non-families. 34.5% of all households were made up of individuals, and 12.1% had someone living alone who was 65 years of age or older. The average household size was 2.08 and the average family size was 2.65. In the CDP, the population was