The first segment of this paper is an overview of recent efforts in the standardization and guide developments by the American Concrete Institute (ACI) Committee 440 on Fiber Reinforcement Polymers for Buildings and by the American Association of State Highway Transportation Officials (AASHTO) for Bridges in the US. This is complemented by details on the most recent large-scale field durability study in the US to autopsy FRP reinforcing bars from eleven bridges constructed with FRP between 15 and 20 years ago. The work provides insight on how the FRP bars have been performed over the last two decades under various filed service conditions through physical and microscopic examination. To assess the performance of bridges' concrete that surrounds the GFRP bars, pH, carbonation depth, and chlorides content were conducted to see if any chemical changes and/or microcracks occurred in the concrete. Scanning electron microscopy (SEM) was performed to observe any microstructural degradations that might take place in both the GFRP and the surrounding concrete including the interfacial transition zone (ITZ). Energy dispersive spectroscopy (EDS) was applied to see if there were any elemental changes. Short bar shear, glass transition temperature, and fiber content testing were conducted on the GFRP samples to evaluate the GFRP's state. No microstructural degradation was observed from the SEM analysis and the EDS did not show any changes in the chemical composition. The measured fiber content from the burn off testing was very close to the pristine values. However, the glass transition temp and short bar shear (SBS) showed some difference when compared to control samples. This study adds new evidence to the validation of the long-term durability of GFRP bars as concrete reinforcing used in field applications.