From the New York Times:
Dead Horse Bay sits at the western edge of a marshland once dotted by more than two dozen horse-rendering plants, fish oil factories and garbage incinerators. From the 1850′s until the 1930′s, the carcasses of dead horses and other animals from New York City streets were used to manufacture glue, fertilizer and other products at the site. The chopped-up, boiled bones were later dumped into the water. The squalid bay, then accessible only by boat, was reviled for the putrid fumes that hung overhead.
As the car industry grew, horse and buggies — thus horse carcasses — became scarce, and by the 1920s, there was only one rendering plant left.
This area used to be called Barren Island, when it was a separate island in Jamaica Bay. Barren Island was connected to the mainland of Brooklyn when landfill was used in 1926 to create Floyd Bennett Field, New York City’s first airport. Filled with trash by the 1930s, the trash heap was capped, only to have the cap burst in the 1950s and the trash spew forth onto the beach. Since then garbage has been leaking continually onto the beach and into the ocean from Dead Horse Bay.
The beach is accessible by bike, via the greenway on Flatbush Avenue on the way to Fort Tilden, as you pass Floyd Bennett Field but before reaching the Marine Parkway-Gil Hodges Memorial Bridge. The best time to go is at low tide.
You can find old bottles such as this Minck soda bottle, a soda apparently produced in Bushwick up until the 1960s.
Other old bits of garbage can be found, such as this fragment of horse bone for which Dead Horse Bay was named.