Mo. Rev. Stat. § 391.230

All street railway companies or corporations operating cars by electricity, or by overhead wires, shall construct and maintain its wires at a height of not less than twenty-two feet above the top of the rail of the railroad track crossed by such street railway company, and the wires of such street railway company shall be guarded, or provided with fenders or guard wires, so as to prevent the same from coming in contact with the cars, track or telegraph line along the track of such railroad company.