Key Largo is a census-designated place and town in Monroe County, Florida, located on the island of Key Largo, in the upper Florida Keys. As of the 2000 census, the town had a total population of 11,886. The name comes from the Spanish Cayo Largo, or 'long key'. It is the first island of the Florida Keys and the originating point of the Overseas Highway to Key West. Key Largo apartments for rent comparison page shows most up to date rent information on Key Largo apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.