From the late 1960s through the mid-1990s, North American commuter railroads electrified with overhead wire moved toward high-voltage alternating current (AC) at commercial frequency so as to adopt state-of-the art technology. The extent and complexity of reelectrification have varied greatly, as projects in New Jersey, Connecticut, and Montreal, Canada, (and one planned for the Netherlands) show. Changes in the justification threshold for reelectrification are reviewed, along with a decision to retain a direct current (DC) system in Chicago. The recent development of onboard inverters, changing DC into AC for traction motors, has made it easier for electric rail operations to enjoy the benefits of AC propulsion without reelectrification costs.