Oysters used to be one of the cheapest and widely available foods in New York City, and crushed oyster shells were even used as mortar to build the city and pave its roads.
Owing to a surge in production at the end of the 19th century, oysters became cheaper than meat, poultry, and fish, making them a popular dish on working class tables in the United States and Europe. This period of mass production is known as the Golden Age of Oysters.
New York is right next to where a giant oyster reef used to be. People used to be able to just walk outside and collect them for dinner. The oysters also cleaned the water and protected the city from storms. Each adult oyster filters 50 gallons of water per day.
Then they ate them all. Now the city is vulnerable to storms and has water pollution problems.
When the first settlers arrived, oysters were so numerous in the Chesapeake Bay that they were able to filter the whole bay about once a week. Their current numbers are less then 1% of what they were at that time.