The PDO (Pacific Decadal Oscillation) and CTI (Cold Tongue Index) indices have been used to represent decadal-scale and ENSO-scale phenomena in the Pacific basin. Both indices appear to be expressed (albeit modestly) in tree-ring chronologies over western North America, which offers the possibility to recover the history of the indices during pre-instrumental time. The spatial correlation pattern of the PDO and CTI with tree-ring chronologies is quite similar over western North America, with a notable exception in Southern California, where the PDO shows positive values while the CTI shows null ones. We used a network of newly developed chronologies for Southern and Baja California to investigate decadal-scale oscillations. The average and the first principal component of all tree-ring chronologies are significantly correlated with the PDO. We have then used the longest chronologies to reconstruct decadal-scale variability over the past four centuries.