I was actually looking for Fort Waldegrave. this marker is at the bottom of the Signal Hill road just about where you turn off the main road for the walking trails that lead out to the old Forts and batteries. Signal Hill was armed intermittently from 1696 to 1945. This is excerpted from an excellent site
Newfoundland Forts:
Several batteries were located here including, Battery Waldegrave (built on the site of the old North Castle Battery) a two-gun battery complementing Chain Rock Battery, Queen's Battery (1796 - 1870) above North Head, Wallace's Battery, Duke of York's Battery (site), and Carronade Battery. All of these were built during the Napoleonic Wars (1800 - 1815). French forces from Placentia captured St. John's in 1696, 1705, and 1709. The French briefly held the town again in 1762. The British (who may have called it Fort St. John's) captured and used the hill to bomb the French-held Fort William. This was the last battle of the French and Indian / Seven Years' War in North America. The British viewed the Hill as a final retreat for Forts William and Townshend. A blockhouse was built here in 1795. It was demolished in 1810 to plan for a Martello Tower, which was never built. New barracks were built on the hill and at Queen's Battery in the 1830's. The Hill was refortified during the American Civil War. British forces left in 1870. The Cabot Tower was built in 1897 for Queen Victoria's birthday celebration. It is not a defensive structure, but may have been used as a lookout.
Fort Waldegrave (the old battery dismantled 1868, rebuilt 1916) was used in World War I (1916 - 1920). The barracks became a dance hall, but were eventually torn down. The two 4.7-inch guns that were here were transferred to Fort Amherst in 1941. The gun area is now a parking lot.
The Americans built two coastal defence batteries here in 1941, each consisting of an 8-inch M1888 gun on a M1918 barbette carriage, located at the present-day parking lot for Cabot Tower. The two guns were removed and relocated to Redcliff Head in 1942. A battery of four 155mm guns on panama mounts was located here, until moved to Middle Cove and Manuels. This position was considered a subpost of Fort Pepperrell