The current study examined how collective bargaining provisions affected average teacher salary trends for states from 1960 to 2000, after controlling for various economic, social, and demographic variables. Results show that collective bargaining had a significant, but waning, effect on teacher pay increases over the 40 year period with slight effects found in the 1970s after the initial organization of unions. Further, results show this effect in certain regions, but not others. Finally, results show that after controlling for other factors, the difference in teacher pay between collective bargaining and non-collective bargaining states has changed little over the last 40 years. Any increases experienced in the collective bargaining states were also experienced in the latter, either simultaneously or shortly thereafter. This study is the first interstate historical comparison of teacher pay that controls for teacher educational attainment and experience over a 40 year period, as well as adjusting for inflation and cost of living. The implications for this comprehensive and innovative approach calls for a refocusing of research on teacher salaries such that these findings combined with other studies of similar rigor and depth will be able to better inform educational policy decisions.