It initially consisted of a single launch rail, from which XSM-73 Bull Goose missiles were tested.

Construction at LC-21 started in 1956, leading to acceptance into military service on 26 February 1957, with Launch Complex 22.

Following the end of Bull Goose test flights, Complex 21 was renovated for the Mace rocket.

This involved the addition of the second launch rail, and the construction of a concrete structure surrounding the complex.

After the last launch, the complex was retained as a backup site until the 1970s, in case a future missile needed to use it.