Building On A Base II

As observed, the Future History, the Psychotechnic History, the Technic History and the Known Space future history have closely parallel pyramidal structures:

several introductory stories providing a base for the rest of the series;
intermediate works systematically building on the base, then on each other;
a story that is the future-most point, thus the pyramid's peak.

Although two further Campbell-edited future histories are not constructed on the Heinlein model, each nevertheless has a distinct "base":

Asimov's I, Robot covers robots, interplanetary exploration and the first use of the hyperdrive;
two stories by James Blish, covering the discoveries of anti-gravity and the anti-agathics, were incorporated into a novel also covering the Fall of the West.

The first eight stories in Poul Anderson's History of Technic Civilization introduce an extraordinary number of elements of the series:

the Jerusalem Catholic Church - some of its members play pivotal roles;
the hyperdrive, which makes interstellar civilization possible;
Ythri;
the planet Gray, later renamed Avalon;
the Polesotechnic League that will rise and fall to be followed by the Troubles, the Empire, the Long Night, the Allied Planets and human civilizations in several spiral arms;
Adzel, who will join Nicholas van Rijn's trader team led by David Falkayn;
van Rijn;
Falkayn who will lead the trader team, rescue Merseia, discover Mirkheim, found Supermetals and colonize Avalon with Ythrians;
several of the races that will join Supermetals.