The last will of a Basque seaman has been discovered in an archive in Spain in which Domingo de Luca asks in 1563, “that my body be buried in this port of Plazençia in the place where those who die here are usually buried.” It is believed to be the oldest original civil document written in Canada.

[3][4] Contemporary scholars think that the land called Vinland extending from Nova Scotia to L'Anse aux Meadows consisted of at least a few settlements;[5] probably on the Avalon Peninsula too.

[7][8] In 1711, the British Rear-Admiral Hovenden Walker considered attacking the French at Placentia with a Royal Navy fleet containing fifteen ships, armed with a total of nine hundred cannons, and transporting 4,000 soldiers.

[11] Three royal ships accompanied by merchant vessels took the French residents of Placentia to the future site of Louisbourg.

[12] For a time in the 18th century, it still rivalled St. John's in size and importance, as evidenced by the future King William IV's summering at Placentia in 1786 and using it as his base of operations when acting as surrogate judge in Newfoundland.

[13] Considering that the population of Newfoundland was reported as 8,000 11 years earlier, in 1775, Placentia's relative size and importance becomes apparent.

In the 18th century there were also a large number of settlers from the Channel Islands, from which Jerseyside, a prominent section of the town, derives its name.

For a time, this was the largest American military base outside of the United States, and it played an integral role in World War II, earning the nickname "the Gibraltar of the Atlantic."

Suddenly, people who had fished all of their lives (engaging in a type of barter called the truck system) had access to good-paying jobs on the American base.

[18] This population decline has been ongoing since the early 1990s; in the 1996 census, Placentia was, proportionately, the 2nd fastest shrinking town in Canada,[19] dropping from 5,515 to 5,013 between 1991 and 1996.

The fisheries of Placentia played a large role in ultimately securing Newfoundland as the world's largest exporter of salt codfish.

[22] After the war of 1689 had set back the colonial fishing industry, Placentia quickly renewed its seasonal fisheries, and in 1698 had sent more than 3,916 tonnes of cod to France.

This, along with the collapse of the Atlantic northwest cod fishery and the moratorium introduced by the Canadian government a few years earlier, left the town of Placentia without an economic base for some time, although recent developments by Vale Inco are beginning to stabilize the town's rocky economic situation.

It has a unique lift-bridge named the Sir Ambrose Shea Lift Bridge that spans the tumultuous tides of 'the gut' (the narrow opening to the harbour).

The primary production is Faces of Fort Royale, performed at Castle Hill National Historic Site, depicting the lives of the early inhabitants of Placentia under the leadership of Governor De Broullion.