  This is the transcript of a talk given at the 3rd Simons Workshop in
Mathematics and Physics on July 26, 2005. We review the genesis of the CHL
(Chaudhuri-Hockney-Lykken) project, explaining both its phenomenological goals
and theoretical justification in light of the known vast proliferation of N=1
string vacua. We explain what a CHL compactification is, review some key
results such as the construction of moduli spaces with a small number of
massless scalar fields, the decompactification of such moduli spaces to one of
five consistent ten-dimensional superstring theories, and the appearance of
electric-magnetic duality in only the four-dimensional moduli spaces, a 1995
observation due to Chaudhuri & Polchinski.
