When President Lincoln authorizes construction of a system that will connect the Union Pacific and Central Pacific railways, a contractor (Will Walling) and a surveyor (George O'Brien) set out to map the best route. Although they find a new pass that promises even greater efficiency than previously hoped for, the risk of attacks on workers from natives threatens to dampen, the spirit of the ambitious project. With its powerful historical theme, and moments of drama, comedy and even tender romance. The Iron Horse deserves its place of honor in the annals of cinema.