Proxy-based reconstructions of the Pacific Decadal Oscillation (PDO) are essential for understanding pre-instrumental variability in this low-frequency oscillation. Multiple reconstructions of the PDO exist but demonstrate weak coherence prior to the 20th century. Analyses of atmospheric moisture and pressure patterns in teleconnected tree-ring sites used for the reconstructions indicate that terrestrial climate impact patterns associated with northern Pacific conditions have been spatially variable over the instrumental period. Tropical Pacific and Northern Hemisphere climate modes influence these surface patterns and are reflected in the PDO reconstructions. Divergence prior to the 20th century calibration period may be due to time-dependent nonlinearities in the PDO and changes in the influence of the El Niño-Southern Oscillation system over time.