Before Columbus and the rise of industrial oyster operations, there was an abundance of oysters in the bay. Oysters first arrived in the Chesapeake 5,000 years ago, and shortly after, local Indians began eating them. Archaeologists found evidence the local Native Americans returned to the same place to collect oysters for 3,000 years. John Smith, on a voyage up the Chesapeake, stated oysters “lay as thick as stones.” In fact, the word Chesapeake derives from an Algonquian word meaning ‘Great Shellfish Bay’. Because of the abundance of oysters filtering the waters of the Chesapeake, the water was much clearer than it is now. Visibility would sometimes reach 20 feet. When the English began settling the area, there is evidence they had a localized impact of the oyster population. One archaeological site measured oyster sizes near Maryland’s old capital St. Mary’s city from 1640 to 1710. In 1640, when the city was still small, oysters measured 80mm, and in the city’s maximum population in 1690, they measured to 40mm. When the capital moved to Annapolis, the population moved with it, and by 1710, the oysters were back up to 80mm. However, the effect of local over harvesting would remain local until after the Civil War, when a combination of new technologies led to the removal of nearly all the bay oysters.
The industrial revolution would introduce several new technologies to the Chesapeake Bay area, which allowed for more intensive oyster harvesting. First, there was the invention of canning. This allowed oysters to be preserved much longer, and created demand for oysters across the world. Secondly, the invention of the dredge enabled oyster harvesters to reach untouched depths of the Chesapeake. And finally, the proliferation of steam-powered ships and railroads made transportation more reliable, enabling merchants to sell oysters far and wide. Estimates for the harvest in 1839 give a figure of 700,000 bushels. After the Civil War, dredges were legalized, and harvesting exploded to 5 million bushels that year. By 1875, 17 million bushels were taken from the bay. The harvesting would reach its peak in the 1880s, with 20 million oysters being harvested from the bay each year. Not only were they being taken for food, but also oyster reefs, where oysters had built hills of their dead shells over thousands of generations, were being dredged out. There were many uses for the surplus oyster shells then. They were ground into mortar, used as filler in roads, and used as a source of lime in agricultural fertilizer. By the 1920s, harvests would be down to just 3-5 million bushels per year because of over harvesting.
Over harvesting would eventually deplete the remaining oyster population in the bay to just 1% of its historical amount, where it stands today. Oyster harvests began to decline in the 1890s. They were being taken much faster than they could reproduce. Also, many of the shells and reefs were being taken and not being replaced. Oyster spat need a hard surface to which to attach, and these were vanishing because of the destruction of oyster reefs. By the 1920s, harvests were down to 3–5 million bushels per year, stabilized for a time by returning oyster shells back to the bay. Today, oyster harvesting on the Potomac is strictly regulated to prevent over harvesting and promote a healthy oyster population.