Miami Beach is really made from the bottom of Biscayne Bay which was dredged by the machines from the recently completed Panama Canal. Before the landfill, Miami Beach was basically a sandbar of watery mangroves.
A fantastic book about the story of Florida is called A Land Remembered by Patrick Smith. It’s a fictional story set in Florida from the Civil War to around 1970. There is a specific timeline in the book about the settlement of Miami and Miami Beach.
Highly recommend it. It’s like James Michner meets Lonesome Dove.
https://www.goodreads.com/book/show/362002.A_Land_Remembered