The bridge construction system and method according to the present invention provides a lightweight, efficient, economical, long-lasting, and easily implemented composite steel structure that can be filled with concrete in place for the construction of pedestrian and smaller road bridges, specifically those found in rural areas. The bridge construction system of the present invention is unique in that it is a steel-frame reinforced composite bridge with decking and rebar caging that provides a permanent, non-removable form for poured-in-place concrete. The composite nature of the bridge allows for installation of the bridge to take place in one day, while the entire process from site preparation such as grading and excavation to cleanup takes a week or less. The quick installation of the bridge is designed to have a minimally invasive impact on the surrounding environment.