The Columbia River Basalt Group (CRBG) eruptions have a well-defined relative magnetostratigraphy but have not been definitively correlated to the geomagnetic polarity time scale. 40 Ar/ 39 Ar ages are presented from lavas erupted in the R 0 through N 1 magnetozones of the CRBG and in the transition between R 0 and N 0 . Four ages from transitionally magnetized lava flows at Steens Mountain, Catlow Peak, and Poker Jim Ridge with a weighted mean age 16.58±0.10Ma 1 1All uncertainties herein are reported at 1standard deviation unless otherwise specified, pursuant to a community-wide consensus (Renne et al., 2009). and the more precise age 16.654±0.025Ma of the normally magnetized Oregon Canyon tuff at the top of the Catlow Peak section show that the oldest CRBG magnetozone (R 0 ) correlates with the C5Cr chron. Bayesian statistical analysis applied to data from four flows at Catlow Peak (using the mean age of the Steens reversal) gives a best and preferred age of the Steens reversal of 16.73+0.13/−0.08Ma (95% confidence). Depending on the geomagnetic polarity time scale model, the eruption rate from N 0 through R 2 (0.34–0.45Ma in the middle and the bulk of the CRBG emplacement) averaged 0.30–0.41km 3 /a and peaked at a rate 1 1/2 to 4 1/2 times higher during R 2.