This paper presents a long-term monitoring campaign for safety assessment of an over 100 years old steel railway bridge in Vänersborg in the southwest of Sweden. Due to its age, the bridge is affected by severe corrosion, and cracks have been detected during inspection. In anticipation of a large-scale reparation of the bridge, a comprehensive monitoring system has been installed. The monitoring system consists of 5 accelerometers, 16 strain gauges, 1 inclinometer and 3 weather measurement sensors (temperature, wind speed and wind direction). Data is collected continuously with high sampling frequency, transmitted to a structured IoT database in the cloud, and used for further processing and visualization. This paper describes the safety assessment processes, the underlying ideas behind them, the challenges encountered, and the developed monitoring dashboard for visualization of results. It also discusses the increased capabilities of the system after an entire year of monitoring.