The first hydrants were used for public water supply from the earliest municipal water systems. They resembled faucets and were at best suited for the bucket brigade method of firefighting. Prior to municipal water systems, there were other means to provide water in the event of a fire.
In the beginning, the original "hydrant" may have been something like this iron cauldron from China Firefighting cauldrons were placed in strategic locations in ancient China and kept filled with water --- at the ready --- in the event of a fire.
In colonial America cisterns were used to store water for early fire fighting purposes, and these continued to be used even after the introduction of the hydrant in many cities. Fire cisterns are underground tanks or structures that hold water to be pumped for firefighting use.
The term "fire plug" dates from the time when water mains were made from hollowed out logs. The fire company (usually volunteers) would head out to the fire, dig up the cobbles down to the main, then bore a hole into the main so that the excavation would fill with water which they could draft using their pumper. When finished fighting the fire, they'd seal the main with -- you guessed it -- a "fire plug". The next time there was a fire in the neighborhood; they'd dig up the plug and not have to cut into the main.
Cast iron would come to replace wooden water mains, and when cast iron started becoming popular, branched fittings were placed on the mains at intervals, much like today's fire hydrants. These were like underground hydrants which could draw water from the water mains in a crude fashion. The first post or pillar type hydrant is generally credited to Mr. Frederick Graff Sr., Chief Engineer of the Philadelphia Water Works around the year 1801. It had a combination hose/faucet outlet and was of "wet barrel" design with the valve in the top.
In 1802, the first order for cast iron hydrants was placed with cannon maker Foxall & Richards. In 1803, Frederick Graff Sr. introduced an improved version of the fire hydrant with the valve in the lower portion. These were inserted into wooden mains with a tapering joint. In 1811, Philadelphia claimed to have 230 wooden hydrant pumps and 185 cast iron fire hydrants.
As late as 1869, the City of Buffalo, NY was still installing wooden case hydrants, according to the first annual report of their public waterworks. But by this time the days of the wooden case hydrant were over. Indeed, by 1865, Philadelphia had installed cast iron hydrants that were very similar to today's models. Three basic types of hydrants were established for connection to the pressurized municipal water supply: the dry barrel, the wet barrel and the below ground or flush type.