Signal Hill dominates the entrance to St. John's harbor, a narrow channel called the Narrows that made the height essential to defense and communication. Indigenous peoples had long used Newfoundland's coasts before European fishing and settlement intensified. By the seventeenth century, English and French rivals contested St. John's because its sheltered harbor supported the Atlantic fishery. Lookouts on the hill could see approaching ships and signal the town, while batteries below attempted to control the entrance with cannon.

The hill's best-known military episode came in 1762 during the Seven Years' War. French forces captured St. John's, and British troops under Lieutenant-Colonel William Amherst advanced to retake it. On 15 September they fought near the summit in the Battle of Signal Hill, forcing the French back toward Fort William and securing surrender soon afterward. The action is often described as the war's final North American battle. Later fortifications, barracks, and gun positions reflected recurring anxiety during wars with France and the United States.

During the nineteenth century, Signal Hill became increasingly important for communications. Flags conveyed the identities and news of ships before they entered harbor, allowing merchants, families, and officials to prepare. The name “Signal Hill” replaced earlier military names through this function. The government began building Cabot Tower in 1897 to commemorate the 400th anniversary of John Cabot's voyage and Queen Victoria's Diamond Jubilee. Completed in 1900, its rugged stone form became a symbol of Newfoundland as a distinct dominion.

On 12 December 1901, Guglielmo Marconi received signals at Signal Hill that he identified as the letter “S” transmitted from Poldhu, Cornwall. The experiment became famous as the first transatlantic wireless reception, though historians have debated the evidence and technical conditions. Marconi's presence nonetheless marked a turning point in public imagination, promising communication beyond cables. Commercial wireless soon developed elsewhere, and the hill continued to host military and communications installations through both world wars.

Newfoundland joined Canada in 1949, changing the political framework around the landmark. Signal Hill was designated a national historic site, and Parks Canada developed interpretation of defense, signaling, wireless, and harbor life. The landscape includes Cabot Tower, Queen's Battery, paths, archaeological remains, and views across the Atlantic. Reconstruction and ceremonial military programs have helped visitors visualize garrison history, while newer interpretation broadens attention to civilian workers, women, Indigenous history, and the fishery that gave the harbor its value.

Today Signal Hill is both an urban open space and a place of national memory. Severe wind, salt, erosion, wildfire risk, visitor pressure, and adjacent development challenge conservation. The skyline and ocean view can make history seem inevitable, but the hill's meaning changed whenever technology or sovereignty changed. It has been lookout, battlefield, flag station, wireless testing ground, wartime post, commemorative landscape, and recreation area. Its enduring significance comes from the human effort to see, defend, and communicate across the Atlantic. The continuing use of its trails and viewpoints keeps that history within everyday life in St. John's. Each ship entering the Narrows still demonstrates why this exposed height mattered to soldiers, merchants, technicians, and waiting families.