Rearming the American coastline with the long range 16-inch weapons from existing army and navy stocks finally got started in the late 1930s. These guns were emplaced in positions with substantial overhead protection. Two 16-inch prototype batteries were con-structed at San Francisco from 1937 to 1940, and a few other batteries were started during this time. A full construction program was authorized by Congress in September of 1940. The program planned for new defense at some 19 harbors along both coasts of North America. The fortifications were built using two standardized designs, a two-gun 16-inch battery (or in some cases remodeled 12-inch batteries) and a two-gun 6-inch battery (or in some cases 8-inch batteries), along with their supporting command and observing stations. When America entered the war in December of 1941, a large number of mobile weapons were rushed to both coasts. A number of other "temporary" seacoast defenses were built using old naval weapons and relocated Army seacoast weapons.
A 16-inch WWII-era battery-Battery Paul D. Bunker (BCN 127) in Los Angeles, CA. (White Point Park, City of Los Angeles)
A WW II-era 6-inch battery-Battery 246, Fort Columbia, WA, north of Astoria, OR. (Fort Columbia State Park)
The seacoast defense construction program went into high gear in 1942, with priority for the sites along the Pacific coast. Batteries of new 90 mm guns were added to the program as anti-motor torpedo boat (AMTB) units. By that year permanent defenses were planned for 33 harbor areas. However, after the Battle of Midway in June of 1942, the possibility of a Japanese attack on the American mainland diminished. As a result the construction program was curtailed in 1944 and halted altogether by 1948.
It was apparent that the day of seacoast artillery was past,
outdated by the airplane, the missile, and new amphibious landing
techniques. By 1950, almost all of the big guns were scrapped,
all the harbor defense commands dismantled and the Coast Artillery
Corps abolished as a separate branch of the army. The old coast
defense reservations were either converted to other uses by the
military or declared surplus.
The first post-seacoast artillery American continental defense system was the Nike surface to air missile (1954-1974).
(Site SF-88, Golden Gate National Recreation Area, Marin Headlands,
CA)