The Cygnus-X region contains a massive star formation complex with the richest known concentration of massive protostars and the largest OB associations in the nearest 2 kpc. The Spitzer Cygnus-X Legacy Survey is an unbiased survey of 24 sq degrees in Cygnus-X with IRAC and MIPS and has the sensitivity to detect young stars to a limit of 0.5 Msolar. This survey is an important step in constructing one of Spitzer's greatest legacies: surveying with high sensitivity and spatial resolution a representative sample of Galactic star forming regions, from Bok globules to complexes containing millions of solar masses of gas and hundreds of O-stars. We present results of a search for infrared dark clouds (IRDCs) in the survey region. The IRDC are regions of high extinction and have been found to be correlated with molecular clouds and often contain objects at the earliest stages of star formation. Until now the IRDCs have been studied using MSX and recently the IRAC GLIMPSE data toward the inner part of the Galaxy; the greater sensitivity of the Cygnus-X survey allows us to better distinguish these objects from the background and characterize them in detail. We are conducting a census of the IRDCs in the survey region, and a search for protostars and associated low-mass star formation. The properties of the IRDCs will be determined, along with their associated clusters of low-mass stars. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory (JPL), California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA and through JPL Contract 1256790.< Réduire