Battery Leary- Merriam was another 14-inch rifle battery on disappearing carriages begun at the same time as Osgood-Farley. It was located a few thousand feet north and east of the former battery and faced to the east-southeast so that its field of fire covered the entrance to the Los Angeles Harbor and down to Bolsa Chica. It was begun on January 20, 1916 and completed on October 10, 1919. It was transferred to the Army on that date at a cost of $251, 362.
Battery Leary's gun was 48-feet 3-inches long, M1910M1 No. 14 made by the Watervliet Arsenal and mounted on May 14,1917 on an M1907M1 disappearing carriage No. 18 built at the Watertown Arsenal.
Merriam's gun was 48-feet 3-inches long, M1910M1, No. 16 constructed at Watervliet Arsenal. It was mounted on April 24, 1917 on an M1907M1 disappearing carriage No. 19 manufactured at the Watertown Arsenal. These were the largest carriages of this type manufactured for the batteries on the west coast.
The Battery was named for Brigadier General Peter Leary, Jr. and Major General Henry C. Merriam.
This Battery served along with Osgood-Farley until 1944 when their guns were declared obsolete. At that time the underground rooms of the battery were converted for use for the Harbor Entrance Command Post (HECP), the Navy's Monitoring post for the ship traffic coming into the harbor, the Harbor Entrance Defense Post, and the Army's command post for the Harbor Defenses of Los Angeles. The battery served also as Fire Control Site No. 6. After the end of World War II, in the 1950s and 1960s, the Leary side of the Battery was taken over for use as the command post and Integrated Fire Control (LA-43C) area for Nike battery LA-43, whose launch facilities were at White Point. The old battery observation stations from the 1920s are located behind the Marine Exchange building, a modern day equivalent of the HECP. The Nike radar domes were on raised platforms located around Leary's gun pit.
Just to the south of Battery Leary is a World War II era base end station.
The Merriam part of the battery was used by an art school and performing arts theater. The gun pit was extensively modified for these purposes.
Report of Completed Works - Seacoast Fortifications