A low cost, low power and reliable bridge structure health monitoring and in-situ inspection system has been developed to detect and track fatigue cracks on steel bridges. It includes a small, low power, multi-channel and multi-sensor data acquisition and processing platform that interfaces with Acoustic Emission (AE), strain gauge and ultrasonic guided wave sensors for damage monitoring on a bridge structure, a miniature gateway node that integrates with IEEE 802.15.4 and Global System for Mobile communications (GSM) radios for wireless data collection and transmission to a remote computer server, and a small solar energy harvesting module for powering the sensor platform and gateway node. The system utilizes (AE) and strain sensors to continuously monitor steel bridge structures for possible damage events such as growth of a fatigue crack, which after initial verification then triggers the ultrasonic guided wave sensors for active inspection of the suspected area. The ultrasonic sensors will also perform scheduled inspections if no triggering event has occurred for a prolonged time interval. Extensive lab and field tests have been conducted on A-36 mild steel Compact-Tension (C-T) coupons for fatigue crack monitoring, and on a concrete deck, multi-beam steel-girder highway bridge for “web gap” types of crack inspection. Data showed that the system can be used to detect and track the growth of the fatigue crack, and the results are consistent, repeatable and reliable. The ultimate objective is to develop a self sufficient, weather proof, and easy for installation and maintenance wireless bridge health monitoring system for long-term bridge integrity assessment at the bridge component level.