Urban transit riders’ use of mobile communication devices has grown markedly in recent years. Studies evaluating the usage of these devices have generally focused on only one or two points in time, limiting their ability to describe long-range trends. To foster insights into this issue, this study evaluated data from 15,531 passenger observations collected on 156 commuter trains on the metropolitan commuter rail system of Chicago, Illinois, from 2010 through 2015. The data show that the rate of technological usage is following an S-shaped pattern among passengers. The share of passengers using mobile communication devices at observed points grew sharpest during the first three years, rising from 25.6% in 2010 to 47.8% in 2013, a compounding annual rate of 23.1%. Between 2013 and 2015, the share rose to 56.2%, an annualized rate of just 8.4%. Over the five-year period, the share of passengers conducting visually-oriented activities on their devices increased at a faster rate than usage as a whole, whereas the share of passengers engaged in audio-only tasks has dropped. Multiple regression analysis shows that the rate of device usage on trains is highest on outbound trips (traveling away from downtown) and positively related to the income associated with the route traveled, with differences of more than five percentage points between lines of varying levels of affluence.