Prior to the early 1950’s Shelter Key was a 97+ acres of low-lying island (on which most of Key Colony Beach is located). There was a sandy beach on the ocean side but most of the land was marginal, even flooded in periods of high tides. Then, Phil Sadowski began dredging around the island, adding to its size and increasing its height to six feet above mean sea level and later built developments on the island. The small island was extended both south and east. Eventually it spread even to the north until the small island had grown to almost 400 acres. Marl from the bayside was dredged and pumped over the land. On the ocean side, Sadowski had purchased the ocean bottom, legal at the time, for a distance of four hundred feet from the shoreline. This was a coral sand bottom which was dredged and pumped in as the final fill on most of the island. It was only after the fill was solid that dredges began cutting in the canals putting the material from the canals over the original fill to bring the island to six feet above mean sea level. Heavy cypress timbers were used to construct seawalls to held back the filled land. The cypress walls had an expected life of 20 years.
Sometime during 1956-1957, residents of Marathon began discussing incorporating the entire area. Mr. Sadowski did not want that to happen so he began the process of incorporating the island into its own city. The Florida Legislature passed legislation in June 1957 allowing incorporation, which locals unanimously passed in September and created the city of Key Colony Beach.