<p>This paper presents the results of field experimentation on a railroad bridge and compares the findings with that from a finite element (FE) model. A series of detailed field experiments were carried out on almost 120-year-old long span truss-bridge using various sensors to determine bridge modal characteristics (natural frequencies, mode-shapes and damping) and displacements. The first few lateral and vertical modes and frequencies of the bridge were identified. A 3-dimensional FE model of the bridge was developed and analyzed, yielding comparable modal characteristics and displacement responses from field tests. Train axle loading frequencies were also determined from the acceleration as well as displacement data, along with analytical relations. The first three field test observed bridge natural frequencies, especially the second lateral and first vertical, matched well with with the FE predictions. The corresponding modal assurance criterion values for the first three modes indicated a strong agreement. Damping ratios were found within practical range across dominant modes. Axle loading frequencies from train passages identified from the field data aligned well with analytical predictions. Additionally, it is shown that knowing the speed of the train, the field-measured displacement versus time profile of the bridge can help identify the train type (various axle/weight configurations) as well as the numbers of cars in the train. The study establishes a strong correlation between FE modeling and field experimentation, enhancing understanding of truss-bridge dynamics under train loads.</p>