Soon after his arrival at Port Jackson, Governor Arthur Phillip estimated the Cadigal population at around 1500 people, although other estimates range from as low as 200 to as high as 4000.
The occupation of the Sydney area by the British and the subsequent introduction of European diseases including smallpox decimated the Eora people and their neighbours. The disastrous 1789 smallpox epidemic is estimated to have killed about 50% of Sydney's indigenous population, and it has been claimed that only three Cadigal people were left alive by 1791, although archaeological evidence suggests that some Cadigal people may have escaped to the Concord area and settled there.