Despite its imposing appearance, Construction 129 was never used - or even completed. It was to have been armed with 2 guns having massive, 16" diameter barrels. Each weapon weighed almost 1,000,000 pounds and could accurately fire a 2,100 pound shell a distance of 27 miles. This fortification was to have been the highest artillery battery in the Bay Area. However, all work on it was stopped in the mid-1940's, shortly after its guns arrived for mounting. The army had found that weapons like those at Construction 129 and similar batteries wouldn't be effective against attack by enemy planes. As a result, the fortification was abandoned.
Its title, "Construction 129", was only a project number — the battery had never officially been named or manned.