The Collider Detector at Fermilab (CDF) is scheduled to begin
recording data from Run II of the Fermilab Tevatron in early 2000.  The
silicon tracking upgrade constitutes both the upgrade to the CDF silicon
vertex detector (SVX II) and the new Intermediate Silicon Layers (ISL) located
at radii just beyond the SVX II.  Here we review the design and prototyping of
all aspects of these detectors including mechanical design, data acquisition,
and a trigger based on silicon tracking.