Marathon
Market InsightsMarathon is a city on Knight's Key, Boot Key, Key Vaca, Fat Deer Key, Long Point Key, Crawl Key and Grassy Key islands in the middle of the Florida Keys, in Monroe County, Florida, United States. As of the 2000 census, the city had a total population of 10,255. As of 2014, the population estimated by the U.S. Census Bureau was 8,708.